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United States Legal Document 

J^" All citizens and residents are hereby advised that 
this is a legally binding document duly incorporated by 
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to criminal or civil penalties under the law. Ignorance of 
the law shall not excuse noncompliance and it is the 
responsibility of the citizens to inform themselves as to 
the laws that are enacted in the United States of America 
and in the states and cities contained therein. "^& 

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NFPA NEC (2011), the National Electrical Code, 
as incorporated and mandated by the States and 
Municipalities of Alabama, Georgia, Iowa, 
Massachusetts, Minnesota, New Jersey, New Mexico, 
North Dakota, Ohio, Oklahoma, Rhode Island, 
Dallas (Texas) , Houston (Texas) , Vermont, 
Wyoming, et. alia. 






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N F P A 7 





NFPA 



National Electrical Code® 

International Electrical Code® Series 



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Copyright ©2010 

National Fire Protection Association® 

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Quincy, Massachusetts 02169-7471 

NFPA, National Fire Protection Association, National Electrical Code, NFPA 70, and NEC 
are registered trademarks of the National Fire Protection Association. 



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Copyright © 2010, National Fire Protection Association®. All Rights Reserved 

NFPA 70® 
National Electrical Code® 

2011 Edition 

This edition of NFPA 70, National Electrical Code, was prepared by the National Electrical Code 
Committee and acted on by NFPA at its June Association Technical Meeting held June 7-10, 2010, in 
Las Vegas, NV. It was issued by the Standards Council on August 5, 2010, with an effective date of 
August 25, 2010, and supersedes all previous editions. 

This edition of NFPA 70 was approved as an American National Standard on August 25, 2010. 

History and Development of the National Electrical Code® 

The National Fire Protection Association has acted as sponsor of the National Electrical Code since 
1911. The original Code document was developed in 1897 as a result of the united efforts of various 
insurance, electrical, architectural, and allied interests. 

In accordance with the provisions of the NFPA Regulations Governing Committee Projects, a 
National Electrical Code Committee Report on Proposals containing proposed amendments to the 2008 
National Electrical Code was published by NFPA in July 2009. This report recorded the actions of the 
various Code-Making Panels and the Correlating Committee of the National Electrical Code Committee 
on each proposal that had been made to revise the 2008 Code. The report was circulated to all members 
of the National Electrical Code Committee and was made available to other interested NFPA members 
and to the public for review and comment. Following the close of the public comment period, the 
Code-Making Panels met, acted on each comment, and reported their action to the Correlating Com- 
mittee. NFPA published the National Electrical Code Committee Report on Comments in March 2010, 
which recorded the actions of the Code-Making Panels and the Correlating Committee on each public 
comment to the National Electrical Code Committee Report on Proposals. The National Electrical Code 
Committee Report on Proposals and the National Electrical Code Committee Report on Comments were 
presented to the 2010 June Association Technical Meeting for adoption. 

NFPA has an Electrical Section that provides particular opportunity for NFPA members interested in 
electrical safety to become better informed and to contribute to the development of the National 
Electrical Code and other NFPA electrical standards. At the Electrical Section Codes and Standards 
Review Session held at the 2010 NFPA Conference and Expo, Section members had opportunity to 
discuss and review the report of the National Electrical Code Committee prior to the adoption of this 
edition of the Code by the Association at its 2010 June Technical Session. 

This 52nd edition supersedes all other previous editions, supplements, and printings dated 1897, 
1899, 1901, 1903, 1904, 1905, 1907, 1909, 1911, 1913, 1915, 1918, 1920, 1923, 1925, 1926, 1928, 
1930 1931, 1933, 1935, 1937, 1940, 1942, 1943, 1947, 1949, 1951, 1953, 1954, 1955, 1956, 1957, 
1958^ 1959^ 1962^ 1965, 1968, 1971, 1975, 1978, 1981, 1984, 1987, 1990, 1993, 1996, 1999, 2002, 
2005, and 2008. 

This Code is purely advisory as far as NFPA is concerned. It is made available for a wide variety of 
both public and private uses in the interest of life and property protection. These include both use in law 
and for regulatory purposes, and use in private self-regulation and standardization activities such as 
insurance underwriting, building and facilities construction and management, and product testing and 
certification. 



NFPA 70, National Electrical Code, NFPA, and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts, 02169. 



CONTENTS 



Contents 



ARTICLE 

90 Introduction 70- 22 

Chapter 1 General 

100 Definitions 70- 26 

I. General 70- 26 

II. Over 600 Volts, Nominal 70- 33 

110 Requirements for Electrical Installations 70- 34 

I. General 70- 34 

II. 600 Volts, Nominal, or Less 70- 37 

III. Over 600 Volts, Nominal 70-40 

IV. Tunnel Installations over 600 Volts, 

Nominal 70- 43 

V. Manholes and Other Electrical 
Enclosures Intended for Personnel 
Entry, All Voltages 70- 44 

Chapter 2 Wiring and Protection 

200 Use and Identification of Grounded 

Conductors 70- 46 

21.0 Branch Circuits 70-48 

I. Genera] Provisions 70- 48 

II. Branch-Circuit Ratings 70- 52 

III. Required Outlets 70- 55 

215 Feeders 70- 59 

220 Branch-Circuit, Feeder, and Service 

Calculations 70- 61 

I. General 70- 61 

II. Branch-Circuit Load Calculations 70- 61 

III. Feeder and Service Load Calculations .... 70- 64 

IV. Optional Feeder and Service Load 

Calculations 70- 67 

V. Farm Load Calculations 70-70 

225 Outside Branch Circuits and Feeders 70-71 

I. General 70- 71 

II. Buildings or Other Structures Supplied 

by a Feeder(s) or Branch CireunTs) 70- 74 

III. Over 600 Volts 70- 76 

230 Services 70- 78 

I. General 70- 78 

II. Overhead Service Conductors 70- 79 

III. Underground Service Conductors 70- 81 

IV Service-Entrance Conductors 70- 81 

V. Service Equipment — General 70- 84 

VI. Service Equipment — Disconnecting 

Means 70- 84 

VII. Service Equipment — Overcurrent 

Protection 70- 86 

VIII. Services Exceeding 600 Volts, 

Nominal 70- 87 

240 Overcurrent Protection 70- 88 

I. General 70- 88 

II. Location 70- 92 

III. Enclosures 70- 95 



ARTICLE 

IV Disconnecting and Guarding 70- 96 

V Plug Fuses, Fuseholders, and Adapters . . . 70- 96 

VI. Cartridge Fuses and Fuseholders 70- 97 

VII. Circuit Breakers 70-97 

VIII. Supervised Industriallnstallations 70- 98 

IX. Overcurrent Protection Over 600 Volts, 

Nominal 70-100 

250 Grounding and Bonding 70-100 

I. General 70-100 

II. System Grounding 70-103 

III. Grounding Electrode System and 

Grounding Electrode Conductor 70-1 1 1 

IV Enclosure, Raceway, and Service 

Cable Connections 70-116 

V Bonding 70-117 

VI. Equipment Grounding and Equipment 

Grounding Conductors 70-120 

VII. Methods of Equipment Grounding 70-125 

VIII. Direct-Current Systems 70- 128 

IX. Instruments, Meters, and Relays 70-129 

X. Grounding of Systems and Circuits of 

over 1 kV 70-129 

280 Surge Arresters, Over 1 kV 70-131 

I- General 70-131 

II. Installation 70-132 

III. Connecting Surge Arresters 70-132 

285 Surge-Protective Devices (SPDs), 1 kV or 

Less 70-133 

I. General 70-133 

II. Installation 70-133 

III. Connecting SPDs 70-133 

Chapter 3 Wiring Methods and Materials 

300 Wiring Methods 70-135 

I. General Requirements 70-135 

II. Requirements for over 600 Volts, 

Nominal 70-145 

310 Conductors for General Wiring 70-147 

I- General 70-147 

II. Installation 70-147 

III Construction S t\iiK rtions 70-168 

312 Cabinets, Cutout Boxes, and Meter Socket 

Enclosures 70-173 

I. Installation 70-174 

II. Construction Specifications 70-175 

314 Outlet, Device, Pull, and Junction Boxes; 
Conduit Bodies; Fittings; and Handhole 
Enclosures 70-177 

I. Scope and General 70-177 

II. Installation 70-177 

III. Construction Specifications 70- 1 84 

IV Pull and Junction Boxes, Conduit 
Bodies mil Handhok Enclosun ; for 
Use on Systems over 600 Volts, 

Nominal 70-185 



70-2 



NATIONAL ELECTRICAL CODE 201 1 Edition 



CONTENTS 



ARTICLE 

320 Armored Cable: Type AC 70-186 

I. General 70-186 

II. Installation 70-186 

III. Construction Specifications 70-187 

322 Flat Cable Assemblies: Type FC 70-1 87 

I. General 70-187 

II. Installation 70-188 

III. Construction 70-188 

324 Flat Conductor Cable: Type FCC 70-189 

I. General 70-189 

II. Installation 70-189 

III. Construction 70-190 

326 Integrated Gas Spacer Cable: Type IGS 70-191 

I. General 70-191 

II. Installation 70-191 

III. Construction Specifications 70—191 

328 Medium Voltage Cable: Type MV 70-1 92 

I. General 70-192 

II. Installation 70-192 

III. Construction Specifications 70-192 

330 Metal-Clad Cable: Type MC 70-192 

I. General 70-192 

II. Installation 70-193 

III. Construction Specifications 70-194 

332 Mineral-Insulated, Metal-Sheathed Cable: 

Type MI 70-194 

I. General 70-194 

II. Installation 70-195 

III. Construction Specifications 70-196 

334 Nonmetallic-Sheathed Cable: Types NM, 

NMC, andNMS 70-196 

I. General 70-196 

II. Installation 70-196 

III. Construction Specifications 70-198 

336 Power and Control Tray Cable: Type TC ....70-198 

I. General 70-198 

II. Installation 70-199 

III. Construction Specifications 70-199 

338 Service-Entrance Cable: Types SE and 

USE 70-200 

I. General 70-200 

II. Installation 70-200 

III. Construction 70-201 

340 Underground Feeder and Branch-Circuit 

Cable: Type UF 70-201 

I. General 70-201 

II. Installation 70-201 

III. Construction Specifications 70-202 

342 Intermediate Metal Conduit: Type IMC 70-202 

I. General 70-202 

II. Installation 70-202 

III. Construction Specifications 70-203 



ARTICLE 

344 Rigid Metal Conduit: Type RMC 70-203 

I. General 70-203 

II. Installation 70-203 

III. Construction Specifications 70-205 

348 Flexible Metal Conduit: Type FMC 70-205 

I. General 70-205 

II. Installation 70-205 

350 Liquidtight Flexible Metal Conduit: Type 

LFMC 70-207 

I. General 70-207 

II. Installation 70-207 

III. Construction Specifications 70-208 

352 Rigid Polyvinyl Chloride Conduit: Type 

PVC 70-208 

I. General 70-208 

II. Installation 70-208 

III. Construction Specifications 70-210 

353 High Density Polyethylene Conduit: Type 

HDPE Conduit 70-211 

I. General 70-211 

"• II. Installation 70-211 

III. Construction Specifications 70-212 

354 Nonmetallic Underground Conduit with 
Conductors: Type NUCC 70-212 

I. General 70-212 

II. Installation 70-212 

III. Construction Specifications 70-213 

355 Reinforced Thermosetting Resin Conduit: 
TypeRTRC 70-213 

I. General 70-213 

II. Installation 70-214 

III. Construction Specifications 70-216 

356 Liquidtight Flexible Nonmetallic Conduit: 
TypeLFNC 70-216 

I. General 70-216 

II. Installation 70-216 

III. Construction Specifications 70-217 

358 Electrical Metallic Tubing: Type EMT 70-218 

I. General 70-218 

II. Installation 70-218 

III. Construction Specifications 70-219 

360 Flexible Metallic Tubing: Type FMT 70-219 

I. General 70-219 

II. Installation 70-219 

III. Construction Specifications 70-220 

362 Electrical Nonmetallic Tubing: Type ENT ...70-220 

I. General 70-220 

II. Installation 70-220 

III. Construction Specifications 70-222 

366 Auxiliary Gutters 70-222 

I. General 70-222 

II. Installation 70-222 

III. Construction Specifications 70-224 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-3 



CONTENTS 



ARTICLE 

368 Busways 70-224 

I. General Requirements 70-224 

II. Installation 70-224 

III. Construction 70-226 

IV. Requirements for Over 600 Volts. 

Nominal 70-226 

370 Cablebus 70-227 

372 Cellular Concrete Floor Raceways 70-228 

374 Cellular Metal Floor Raceways 70-229 

I. Installation 70-229 

II. Construction Specifications 70-229 

376 Metal Wireways 70-230 

I. General 70-230 

II. Installation 70-230 

III. Construction Specifications 70-231 

378 Nonmetal lie Wireways 70-231 

I. General 70-231 

II. Installation 70-231 

III. Construction Specifications 70-232 

380 Multioutlet Assembly 70-232 

I. General 70-232 

II. Installation 70-232 

382 Nonmetallic Extensions 70-233 

I. General 70-233 

II. Installation 70-233 

III. Construction Specifications 

(Concealable Nonmetallic Extensions 

Only) 70-234 

384 Strut-Type Channel Raceway 70-235 

I. General 70-235 

II. Installation 70-235 

III. Construction Specifications 70-236 

386 Surface Metal Raceways 70-236 

I. General 70-236 

II. Installation 70-236 

III. Construction Specifications 70-237 

388 Surface Nonmetallic Raceways 70-237 

I. General 70-237 

II. Installation 70-237 

III. Construction Specifications 70-238 

390 Underfloor Raceways 70-238 

392 Cable Trays 70-239 

I. General 70-239 

II. Installation 70-239 

III. Construction Specifications 70-246 

394 Concealed Knob-and-Tube Wiring 70-246 

I. General 70-246 

II. Installation 70-246 

III. Construction Specifications 70-247 

396 Messenger-Supported Wiring 70-247 

I. General 70-247 

II. Installation 70-248 



ARTICLE 

398 Open Wiring on Insulators 70-248 

I. General 70-248 

II. Installation 70-248 

III. Construction Specifications 70-250 

399 Outdoor Overhead Conductors over 600 

Volts 70-250 

Chapter 4 Equipment for General Use 

400 Flexible Cords and Cables 70-251 

I. General 70-251 

II. Construction Specifications 70-260 

III. Portable Cables Over 600 Volts, 

Nominal 70-261 

402 Fixture Wires 70-262 

404 Switches 70-266 

I. Installation 70-266 

II. Construction Specifications 70-270 

406 Receptacles, Cord Connectors, and 

Attachment Plugs (Caps) 70-270 

408 Switchboards and Panelboards 70-274 

I. General 70-274 

II. Switchboards 70-275 

III. Panelboards 70-276 

IV. Construction Specifications 70-277 

409 Industrial Control Panels 70-278 

I. General 70-278 

II. Installation 70-278 

III. Construction Specifications 70-279 

410 Luminaires, Lampholders, and Lamps 70-280 

I. General 70-280 

II. Luminaire Locations 70-28 1 

HI. Provisions at Luminaire Outlet Boxes, 

Canopies, and Pans 70-282 

IV. Luminaire Supports 70-282 

V Grounding 70-283 

VI. Wiring of Luminaires 70-283 

VII. Construction of Luminaires 70-285 

VIII. Installation of Lampholders 70-285 

I:X. Lamps and Auxiliary Equipment 70-285 

X. Special Provisions for Flush and 

Recessed Luminaires 70-286 

XI. Construction of Flush and Recessed 

Luminaires 70-286 

XII. Special Provisions for 

Electric-Discharge Lighting Systems of 

1000 Volts or Less 70-286 

XIII. Special Provisions for 
Electric-Discharge Lighting Systems of 

More Than 1000 Volts 70-288 

XIV. Lighting Track 70-289 

XV. Decorative Lighting and Similar 

Accessories 70-289 

411 Lighting Systems Operating at 30 Volts or 

Less 70-289 

422 Appliances 70-290 

I. General 70-290 



70-4 



NATIONAL ELECTRICAL CODE 201 1 Edition 



CONTENTS 



ARTICLE 

II. Installation 70-290 

III. Disconnecting Means 70-293 

IV. Construction 70-294 

V. Marking 70-295 

424 Fixed Electric Space-Heating Equipment 70-295 

I. General 70-295 

II. Installation 70-296 

III. Control and Protection of Fixed 

Electric Space-Heating Equipment 70-296 

IV. Marking of Heating Equipment 70-298 

V. Electric Space-Heating Cables 70-298 

VI. Duct Heaters 70-300 

VII. Resistance-Type Boilers 70-300 

VIII. Electrode-Type Boilers 70-301 

IX. Electric Radiant Heating Panels and 

Heating Panel Sets 70-302 

426 Fixed Outdoor Electric Deicing and 
Snow-Melting Equipment 70-304 

I. General 70-304 

II. Installation 70-305 

III. Resistance Heating Elements 70-305 

IV. Impedance Heating 70-306 

V Skin-Effect Heating 70-306 

VI. Control and Protection 70-307 

427 Fixed Electric Heating Equipment for 

Pipelines and Vessels 70-307 

I. General 70-307 

II. Installation 70-308 

III. Resistance Heating Elements 70-308 

IV. Impedance Heating 70-309 

V Induction Heating 70-309 

VI. Skin-Effect Heating 70-309 

VII. Control and Protection 70-309 

430 Motors, Motor Circuits, and Controllers 70-310 

I. General 70-310 

II. Motor Circuit Conductors 70-316 

III. Motor and Branch-Circuit Overload 

Protection 70-319 

IV. Motor Branch-Circuit Short-Circuit 

and Ground-Fault Protection 70-322 

V. Motor Feeder Short-Circuit and 

Ground-Fault Protection 70-325 

VI. Motor Control Circuits 70-326 

VII. Motor Controllers 70-327 

VIII. Motor Control Centers 70-329 

IX. Disconnecting Means 70-330 

X. Adjustable-Speed Drive Systems 70-333 

XL Over 600 Volts, Nominal 70-334 

XII. Protection of Live Parts — All 

Voltages 70-335 

XIII. Grounding — All Voltages 70-335 

XIV. Tables 70-336 

440 Air-Conditioning and Refrigerating 

Equipment 70-340 

I. General 70-340 

II. Disconnecting Means 70-342 

III. Branch-Circuit Short-Circuit and 
Ground-Fault Protection 70-343 

IV. Branch-Circuit Conductors 70-344 



ARTICLE 

V. Controllers for Motor-Compressors 70-344 

VI. Motor-Compressor and Branch-Circuit 

Overload Protection 70-345 

VII. Provisions for Room Air Conditioners .... 70-346 

445 Generators 70-347 

450 Transformers and Transformer Vaults 

(Including Secondary Ties) 70-348 

I. General Provisions 70-348 

II. Specific Provisions Applicable to 

Different Types of Transformers 70-352 

III. Transformer Vaults 70-354 

455 Phase Converters 70-355 

I. General 70-355 

II. Specific Provisions Applicable to 

Different Types of Phase Converters 70-356 

460 Capacitors 70-357 

I. 600 Volts, Nominal, and Under 70-357 

II. Over 600 Volts, Nominal 70-358 

470 Resistors and Reactors 70-358 

I. 600 Volts, Nominal, and Under 70-358 

II. Over 600 Volts, Nominal 70-359 

480 Storage Batteries 70-359 

490 Equipment, Over 600 Volts, Nominal 70-360 

I. General 70-360 

II. Equipment — Specific Provisions 70-361 

III. Equipment — Metal-Enclosed Power 
Switchgear and Industrial Control 

Assemblies 70-363 

IV Mobile and Portable Equipment 70-365 

V. Electrode-Type Boilers 70-366 

Chapter 5 Special Occupancies 

500 Hazardous (Classified) Locations, Classes 

I, II, and III, Divisions I and 2 70-367 

501 Class I Locations 70-376 

I. General 70-376 

II. Wiring 70-376 

III. Equipment 70-381 

502 Class II Locations 70-386 

I. General 70-386 

II. Wiring 70-386 

III. Equipment 70-388 

503 Class III Locations 70-391 

I. General 70-391 

II. Wiring 70-391 

III. Equipment 70-392 

504 Intrinsically Safe Systems 70-394 

505 Zone 0, 1, and 2 Locations 70-397 

506 Zone 20, 21, and 22 Locations for 
Combustible Dusts or Ignitible 

Fibers/Flyings 70^112 

510 Hazardous (Classified) Locations — 

Specific 70^419 



2011 Edition NATIONAL ELECTRICAL CODE 



70-5 



CONTENTS 



ARTICLE 

511 Commercial Garages, Repair and Storage .... 70-419 

513 Aircraft Hangars 7(M-22 

514 Motor Fuel Dispensing Facilities 70-425 

515 Bulk Storage Plants 70-429 

516 Spray Application, Dipping, and Coating 

Processes 70-434 

517 Health Care Facilities 70-440 

I. General 70-440 

II. Wiring and Protection 70-442 

III. Essential Electrical System 70-445 

IV. Inhalation Anesthetizing Locations 70-45 2 

V. X-Ray Installations 70-455 

VI. Communications, Signaling Systems, 
Data Systems, Fire Alarm Systems, 
and Systems Less Than 120 Volts, 

Nominal 70-456 

VII. Isolated Power Systems 70-457 

5 1 8 Assembly Occupancies 70^458 

520 Theaters, Audience Areas of Motion 
Picture and Television Studios, 

Performance Areas, and Similar Locations ... 70-459 

I. General 70-459 

II. Fixed Stage Switchboards 70-461 

III. Fixed Stage Equipment Other Than 
Switchboards 70-462 

IV. Portable Switchboards on Stage 70-463 

V. Portable Stage Equipment Other Than 

Switchboards 70-466 

VI. Dressing Rooms 70-468 

VII. Grounding 70-468 

522 Control Systems for Permanent 

Amusement Attractions 70-468 

I. General 70-468 

II. Control Circuits 70-468 

III. Control Circuit Wiring Methods 70-469 

525 Carnivals, Circuses, Fairs, and Similar 

Events 70-470 

I. General Requirements 70-470 

II. Power Sources 70-470 

III. Wiring Methods 70-471 

IV Grounding and Bonding 70-472 

530 Motion Picture and Television Studios 

and Similar Locations 70-472 

I. General 70-472 

II. Stage or Set 70-473 

III. Dressing Rooms 70-475 

IV. Viewing, Cutting, and Patching Tables .... 70-475 
V. Cellulose Nitrate Film Storage Vaults 70-475 

VI. Substations 70-475 

540 Motion Picture Projection Rooms 70-476 

I. General 70-476 

II. Equipment and Projectors of the 

Professional Type 70-476 

III. Nonprofessional Projectors 70^177 



ARTICLE 

IV Audio Signal Processing, 

Amplification, and Reproduction 

Equipment 70-477 

545 Manufactured Buildings 70-477 

547 Agricultural Buildings 70-478 

550 Mobile Homes, Manufactured Homes, and 

Mobile Home Parks 70-481 

1. General 70-481 

II. Mobile and Manufactured Homes 70-482 

III. Services and Feeders 70-489 

551 Recreational Vehicles and Recreational 

Vehicle Parks 70-490 

I. General 70-490 

II. Combination Electrical Systems 70-491 

III. Other Power Sources 70-492 

IV Nominal 120- Volt or 120/240- Volt 

Systems 70-493 

V Factory Tests 70-500 

VI. Recreational Vehicle Parks 70-500 

552 Park Trailers 70-503 

I. General 70-503 

II. Low-Voltage Systems 70-503 

III. Combination Electrical Systems 70-504 

IV Nominal 120- Volt or 120/240- Volt 

Systems 70-505 

V Factory Tests 70-511 

553 Floating Buildings 70-512 

I. General 70-512 

II. Services and Feeders 70-512 

III. Grounding 70-512 

555 Marinas and Boatyards 70-5 1 3 

590 Temporary Installations 70-516 

Chapter 6 Special Equipment 

600 Electric Signs and Outline Lighting 70-5 1 9 

I. General 70-519 

II. Field-Installed Skeleton Tubing* 
Outline 1 ighfing, iu.1 Vcondary 

Wiring 70-523 

604 Manufactured Wiring Systems 70-525 

605 Office Furnishings (Consisting of Lighting 
Accessories and Wired Partitions) 70-526 

610 Cranes and Hoists 70-527 

I. General 70-527 

II. Wiring 70-527 

III. Contact Conductors 70-530 

IV. Disconnecting Means 70-53 1 

V. Overcurrent Protection 70-53 1 

VI. Control 70-532 

VII. Grounding 70-532 

620 Elevators, Dumbwaiters, Escalators, 
Moving Walks, Platform Lifts, and 

Stairway Chairlifts 70-532 

I. General 70-532 



70-6 



NATIONAL ELECTRICAL CODE 201 1 Edition 



CONTENTS 



ARTICLE 

II. Conductors 70-534 

III. Wiring 70-536 

IV. Installation of Conductors 70-538 

V. Traveling Cables 70-539 

VI. Disconnecting Means and Control 70-540 

VII. Overcurrent Protection 70-542 

VIII. Machine Rooms, Control Rooms, 

Machinery Spaces, and Control Spaces .... 70-542 

IX. Grounding 70-543 

X. Emergency and Standby Power 

Systems 70-543 

625 Electric Vehicle Charging System 70-543 

I. General 70-543 

II. Wiring Methods 70-544 

III. Equipment Construction 70-544 

IV. Control and Protection 70-545 

V Electric Vehicle Supply Equipment 

Locations 70-545 

626 Electrified Truck Parking Spaces 70-547 

I. General 70-547 

II. Electrified Truck Parking Space 

Electrical Wiring Systems 70-548 

III. Electrified Truck Parking Space Supply 
Equipment 70-549 

IV. Transport Refrigerated Units (TRUs) 70-551 

630 Electric Welders 70-552 

I. General 70-552 

II. Arc Welders 70-552 

III. Resistance Welders 70-553 

IV Welding Cable 70-554 

640 Audio Signal Processing, Amplification, 

and Reproduction Equipment 70-554 

I. General 70-554 

II. Permanent Audio System Installations .... 70-557 
III. Portable and Temporary Audio System 

Installations 70-558 

645 Information Technology Equipment 70-559 

647 Sensitive Electronic Equipment 70-563 

650 Pipe Organs 70-564 

660 X-Ray Equipment 70-565 

I. General 70-565 

II. Control 70-566 

III. Transformers and Capacitors 70-566 

IV Guarding and Grounding 70-566 

665 Induction and Dielectric Heating 

Equipment 70-567 

I. General 70-567 

II. Guarding, Grounding, and Labeling 70-568 

668 Electrolytic Cells 70-568 

669 Electroplating 70-571 

670 Industrial Machinery 70-572 

675 Electrically Driven or Controlled 

Irrigation Machines 70-573 

I. General 70-573 

II. Center Pivot Irrigation Machines 70-575 



ARTICLE 

680 Swimming Pools, Fountains, and Similar 

Installations 70-575 

I. General 70-575 

II. Permanently Installed Pools 70-579 

III. Storable Pools 70-585 

IV Spas and Hot Tubs 70-586 

V. Fountains 70-588 

VI. Pools and Tubs for Therapeutic Use 70-589 

VII. Hydromassage Bathtubs 70-590 

682 Natural and Artificially Made Bodies of 

Water 70-590 

I. General 70-590 

II. Installation 70-591 

III. Grounding and Bonding : 70-592 

685 Integrated Electrical Systems 70-592 

I. General 70-592 

II. Orderly Shutdown 70-593 

690 Solar Photovoltaic (PV) Systems , 70-593 

I. General 70-593 

II. Circuit Requirements 70-597 

III. Disconnecting Means 70-599 

IV. Wiring Methods 70-601 

V. Grounding 70-603 

VI. Marking 70-604 

VII. Connection to Other Sources 70-605 

VIII. Storage Batteries 70-605 

IX. Systems over 600 Volts 70-607 

692 Fuel Cell Systems 70-607 

I. General 70-607 

II. Circuit Requirements 70-608 

III. Disconnecting Means 70-608 

IV Wiring Methods 70-609 

V Grounding 70-609 

VI. Marking 70-609 

VII. Connection to Other Circuits 70-609 

VIII. Outputs Over 600 Volts 70-609 

694 Small Wind Electric Systems 70-610 

I. General 70-610 

II Circuit Requirements 70-611 

III. Disconnecting Means 70-612 

IV. Wiring Methods .'.' 70-613 

V. Grounding 70-613 

VI. Marking 70-614 

VII. Connection to Other Sources 70-6 1 4 

VIII. Storage Batteries 70-614 

IX. Systems over 600 Volts 70-616 

695 Fire Pumps 70-616 

Chapter 7 Special Conditions 

700 Emergency Systems 70-622 

I. General 70-622 

II. Circuit Wiring 70-623 

III. Sources of Power 70-624 

IV Emergency System Circuits for 

Lighting and Power 70-626 

V. Control — Emergency Lighting 

Circuits 70-626 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-7 



CONTENTS 



ARTICLE 

VI. Overcurrent Protection 70-627 

70 1 Legally Required Standby Systems 70-627 

I. General 70-627 

II. Circuit Wiring 70-628 

III. Sources of Power 70-628 

IV. Overcurrent Protection 70-630 

702 Optional Standby Systems 70-630 

I. General 70-630 

II. Wiring 70-631 

705 Interconnected Electric Power Production 

Sources 70-631 

I. General 70-631 

II. Utility-Interactive Inverters 70-634 

III. Generators 70-635 

708 Critical Operations Power Systems 

(COPS) 70-635 

I. General 70-636 

II. Circuit Wiring and Equipment 70-637 

III. Power Sources and Connection 70-638 

IV. Overcurrent Protection 70-640 

V. System Performance and Analysis 70-640 

720 Circuits and Equipment Operating at Less 

Than 50 Volts 70-640 

725 Class 1, Class 2, and Class 3 

Remote-Control, Signaling, and 

Power-Limited Circuits 70-641 

I. General 70-641 

II. Class 1 Circuits 70-642 

III. Class 2 and Class 3 Circuits 70-644 

IV Listing Requirements 70-648 

727 Instrumentation Tray Cable: Type ITC 70-650 

760 Fire Alarm Systems 70-651 

I. General 70-651 

II. Non-Power-Limited Fire Alarm 

(NPLFA) Circuits 70-652 

III. Power-Limited Fire Alarm (PLFA) 

Circuits 70-654 

IV. Listing Requirements 70-657 

770 Optical Fiber Cables and Raceways 70-660 

I. General 70-660 

II. Cables Outside and Entering Buildings ... 70-661 

III. Protection 70-661 

IV. Grounding Methods 70-661 

V. Installation Methods Within Buildings .... 70-663 

VI. Listing Requirements 70-666 

Chapter 8 Communications Systems 

800 Communications Circuits 70-669 

I. General 70-669 

II. Wires and Cables Outside and 

Entering Buildings 70-670 

III. Protection 70-672 

IV. Grounding Methods 70-673 

V. Installation Methods Within Buildings ... 70-675 

VI. Listing Requirements 70-680 



ARTICLE 

8 1 Radio and Television Equipment 70-682 

I. General 70-682 

II. Receiving Equipment — Antenna 

Systems 70-682 

III. Amateur and Citizen Band 

Transmitting and Receiving Stations 

— Antenna Systems 70-685 

IV Interior Installation — Transmitting 

Stations 70-686 

820 Community Antenna Television and Radio 

Distribution Systems 70-686 

I. General 70-686 

II. Coaxial Cables Outside and Entering 

Buildings 70-687 

III. Protection 70-688 

IV Grounding Methods 70-689 

V Installation Methods Within Buildings .... 70-690 
VI. Listing Requirements 70-693 

830 Network-Powered Broadband 

Communications Systems 70-695 

I. General 70-695 

II. Cables Outside and Entering Buildings . . . 70-697 

III. Protection 70-699 

IV. Grounding Methods 70-701 

V Installation Methods Within Buildings .... 70-702 
VI. Listing Requirements 70-705 

840 Premises-Powered Broadband 

Communications Systems 70-707 

I. General 70-707 

II. Cables Outside and Entering Buildings ... 70-708 

III. Protection 70-709 

IV Grounding VI mods 70-709 

V. Installation Methods Within Buildings .... 70-709 

"i 1 "Lin: . t, iidii nt> 70-710 



Chapter 9 Tables 

TABLES 

1 Percent of Cross Section of Conduit and 

Tubing for Conductors 70-711 

2 Radius of Conduit and Tubing Bends 70-711 

4 Dimensions and Percent Area of Conduit 
and Tubing 

(Areas of Conduit or Tubing for the 

Combinations of Wires Permitted in Table 

1, Chapter 9) 70-712 

5 Dimensions of Insulated Conductors and 

Fixture Wires 70-716 

5A Compact Copper and Aluminum Building 

Wire Nominal Dimensions* and Areas 70-720 

8 Conductor Properties 70-721 

9 Alternating-Current Resistance and 
Reactance for 600- Volt Cables, 3-Phase, 
60 Hz, 75°C (167°F) — Three Single 

Conductors in Conduit 70-722 

10 Conductor Stranding 70-723 



70-8 



NATIONAL ELECTRICAL CODE 2011 Edition 



CONTENTS 



TABLES 

11(A) 
1KB) 
12(A) 
12(B) 



Class 2 and Class 3 Alternating-Current 

Power Source Limitations 70-724 

Class 2 and Class 3 Direct-Current Power 

Source Limitations 70-725 

PLFA Alternating-Current Power Source 

Limitations 70-726 

PLFA Direct-Current Power Source 

Limitations 70-726 

Informative Annex A Product Safety 

Standards 70-727 

Informative Annex B Application Information 

for Ampacity Calculation 70-730 

Informative Annex C Conduit and Tubing Fill 
Tables for Conductors and Fixture Wires of the 
Same Size 70-744 



Informative Annex D Examples 70-804 

Informative Annex E Types of Construction . 70-814 

Informative Annex F Availability and Reliability 
for Critical Operations Power Systems; and 
Development and Implementation of Functional 
Performance Tests (FPTs) for Critical 
Operations Power Systems 70-816 

Informative Annex G Supervisory Control and 

Data Acquisition (SCADA) 70-819 

Informative Annex H Administration and 
Enforcement 70-82 1 

Informative Annex 1 Recommended Tightening 
Torque Tables from UL Standard 486A-B .... 70-828 

Index 70-830 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-9 



NATIONAL ELECTRICAL CODE COMMITTEE 



NATIONAL ELECTRICAL CODE COMMITTEE 

These lists represent the membership at the time the Committee was balloted on the final text of this edition. Since that 
time, changes in the membership may have occurred. A key to classifications is found at the back of this document. 

Technical Correlating Committee 

James W. Carpenter, Chair 
International Association of Electrical Inspectors, NC [E] 
Rep. International Association of Electrical Inspectors 

Mark W. Earley, Secretary 
National Fire Protection Association, MA 
(nonvoting) 

Jean A. O'Connor, Recording Secretary 
National Fire Protection Association, MA 
(nonvoting) 



James E. Brunssen, Telcordia, NJ [UT] 

Rep. Alliance for Telecommunications Industry Solutions 
Merton W. Bunker, Jr., US Department of State, VA [U] 

(VL to Document: 110, Document: 111, Document: 70, 

Document: 70B, Document: 70E, Document: 79, 

Document: 790, Document: 791) 
James M. Daly, General Cable, NJ [M] 

Rep. National Electrical Manufacturers Association 
William R. Drake, Actuant Electrical, CA [M] 
Stanley J. Folz, Morse Electric Company, NV [IM] 

Rep. National Electrical Contractors Association 
Palmer L. Hickman, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 
David L. Hittinger, Independent Electrical Contractors of 
Greater Cincinnati, OH [IM] 

Rep. Independent Electrical Contractors, Inc. 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 
Neil F. LaBrake, Jr., National Grid, NY [UT] 

Rep. Electric Light & Power Group/EEI 
Danny Liggett, DuPont Engineering, Inc., TX [U] 

Rep. American Chemistry Council 

Alternates 
Thomas L. Adams, Engineering Consultant, IL [UT] 

(Alt. to Neil F. LaBrake, Jr.) 

Rep. Electric Light & Power Group/EEI 
Lawrence S. Ayer, Biz Com Electric, Inc., OH [IM] 

(Alt. to David L. Hittinger) 

Rep. Independent Electrical Contractors, Inc. 



Larry D. Cogburn, Cogburn Bros, Inc., FL [IM] 

(Alt. to Stanley J. Folz) 

Rep. National Electrical Contractors Association 
James T. Dollard, Jr., IBEW Local Union 98, PA [L] 

(Alt. to Palmer L. Hickman) 

Rep. International Brotherhood of Electrical Workers 
Ernest J. Gallo, Telcordia Technologies, Inc., NJ [UT] 

(Alt. to James E. Brunssen) 

Rep. Alliance for Telecommunications Industry Solutions 
Daniel J. Kissane, Legrand/Pass & Seymour, NY [M] 

(Alt. to James M. Daly) 

Rep. National Electrical Manufacturers Association 
Michael E. McNeil, FMC Bio Polymer, ME [U] 

(Alt. to Danny Liggett) 

Rep. American Chemistry Council 
Mark C. Ode, Underwriters Laboratories Inc., AZ [RT] 

(Alt. to John R. Kovacik) 
Richard P. Owen, Oakdale, MN [E] 

(Alt. to James W. Carpenter) 

Rep. International Association of Electrical Inspectors 

Nonvoting 

Richard G. Biermann, Biermann Electric Company, Inc., 
IA [IM] 

(Member Emeritus) 
David Mascarenhas, Canadian Standards Association, 
Canada [RT] 

D. Harold Ware, Libra Electric Company, OK [IM] 
Mark W. Earley, NFPA Staff Liaison 



Committee Scope: This Committee shall have primary responsibility for documents on minimizing the risk of 
electricity as a source of electric shock and as a potential ignition source of fires and explosions. It shall also be 
responsible for text to minimize the propagation of fire and explosions due to electrical installations. 

CODE-MAKING PANEL NO. 1 

Articles 90, 100, 110, Chapter 9, Table 10, Annex A, Annex H, Annex I 

Gil Moniz, Chair 
National Electrical Manufacturers Association, MA [M] 



Michael A. Anthony, University of Michigan, MI [U] 

Rep. Association of Higher Education Facilities Officers 
Louis A. Barrios, Shell Global Solutions, TX [U] 

Rep. American Chemistry Council 
Kenneth P. Boyce, Underwriters Laboratories Inc., IL [RT] 
William T. Fiske, Intertek Testing Services, NY [RT] 
H. Landis Floyd, The DuPont Company, DE [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Palmer L. Hickman, National Joint Apprentice & Training 
Committee, MD [L] 

Rep. International Brotherhood of Electrical Workers 



David L. Hittinger, Independent Electrical Contractors of 
Greater Cincinnati, OH [IM] 

Rep. Independent Electrical Contractors, Inc. 
Neil F. LaBrake, Jr., National Grid, NY [UT] 

Rep. Electric Light & Power Group/EEI 
Randall R. McCarver, Telcordia Technologies, Inc., NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 
Harry J. Sassaman, Forest Electric Corporation, NJ [IM] 

Rep. National Electrical Contractors Association 



70-10 



NATIONAL ELECTRICAL CODE 201 1 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Alternates 
Thomas L. Adams, Engineering Consultant, IL [UT] 

(Alt. to Neil F. LaBrake, Jr.) 

Rep. Electric Light & Power Group/EEI 
Joseph F. Andre, National Electrical Manufacturers 
Association, WA [M] 

(Alt. to Gil Moniz) 

Rep. National Electrical Manufacturers Association 
Mark Christian, National Joint Apprentice & Training 
Committee, MD [L] 

(Alt. to Palmer L. Hickman) 

Rep. International Brotherhood of Electrical Workers 
Benjamin F. Dunford, Ben Dunford Electric Company Inc., 
TN [IM] 

(Alt. to David L. Hittinger) 

Rep. Independent Electrical Contractors, Inc. 
Ernest J. Gallo, Telcordia Technologies, Inc., NJ [U] 

(Alt. to Randall R. McCarver) 

Rep. Alliance for Telecommunications Industry Solutions 



Thomas R. Lichtenstein, Underwriters Laboratories Inc., 
IL [RT] 

(Alt. to Kenneth P. Boyce) 
Donald H. McCullough, II, Washington Savannah River 
Company, SC [U] 

(Alt. to H. Landis Floyd) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Susan Newman Scearce, State of Tennessee, TN [E] 

(Voting Alt. to IAEI Rep.) 

Rep. International Association of Electrical Inspectors 
James F. Pierce, Intertek Testing Services, OR [RT] 

(Alt. to William T, Fiske) 

Nonvoting 

Ark Tsisserev, City of Vancouver, Canada [SE] 
Rep. CSA/Canadian Electrical Code Committee 



CODE-MAKING PANEL NO. 2 
Articles 210, 215, 220, Annex D Examples Dl through D6 

Raymond W. Weber, Chair 
State of Wisconsin, WI [E] 
Rep. International Association of Electrical Inspectors 



Richard W. Becker, Engineered Electrical Systems, Inc., 
WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Charles L. Boynton, The DuPont Company, TX [U] 

Rep. American Chemistry Council 
Frank Coluccio, New York City Department of Buildings, 
NY [E] 

Thomas L. Harman, University of Houston-Clear Lake, 
TX [SE] 
Donald M. King, IBEW Local Union 313, DE [L] 

Rep. International Brotherhood of Electrical Workers 
Robert L. LaRocca, Underwriters Laboratories Inc., NY [RT] 
Steven Orlowski, National Association of Home Builders, 
DC [U] 
Jim Pauley, Square D Company/Schneider Electric, KY [M] 

Rep. National Electrical Manufacturers Association 
Ronald L. Purvis, Sharpsburg, GA [UT] 

Rep. Electric Light & Power Group/EEI 
Robert G. Wilkinson, IEC Texas Gulf Coast, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Thomas H. Wood, Cecil B. Wood, Inc., IL [IM] 

Rep. National Electrical Contractors Association 

Alternates 
Jacob G. Benninger, Cornell University, NY [L] 
(Alt. to Donald M. King) 
Rep. International Brotherhood of Electrical Workers 



Lawrence Brown, National Association of Home Builders, 
DC [U] 

(Alt. to Steven Orlowski) 
Paul Crivell, Camp, Dresser, & McKee Inc., WA [U] 

(Alt. to Richard W. Becker) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David A. Dini, Underwriters Laboratories Inc., IL [RT] 

(Alt. to Robert L. LaRocca) 
Daniel J. Kissane, Pass & Seymour/Legrand, NY [M] 

(Alt. to Jim Pauley) 

Rep. National Electrical Manufacturers Association 
William Ross McCorcle, American Electric Power, OK [UT] 

(Alt. to Ronald L. Purvis) 

Rep. Electric Light & Power Group/EEI 
William J. McGovern, City of Piano, TX [E] 

(Alt. to Raymond W. Weber) 

Rep. International Association of Electrical Inspectors 
Stephen V. St. Croix, 1st Electric, Inc., MD [IM] 

(Alt. to Robert G. Wilkinson) 

Rep. Independent Electrical Contractors, Inc. 

Nonvoting 

William Burr, Canadian Standards Association, Canada [RT] 
Douglas A. Lee, US Consumer Product Safety Commission, 
MD [C] 

Andrew M. Trotta, US Consumer Product Safety 
Commission, MD [C] 

(Alt. to Douglas A. Lee) 



CODE-MAKING PANEL NO. 3 

Articles 300, 590, 720, 725, 727, 760, Chapter 9, Tables 11(A) and (B), Tables 12(A) and (B) 

Paul J. Casparro, Chair 
Scranton Electricians JATC, PA [L] 
Rep. International Brotherhood of Electrical Workers 



Lawrence S. Ayer, Biz Com Electric, Inc., OH [IM] 
Rep. Independent Electrical Contractors, Inc. 

Thomas F. Connaughton, Intertek Testing Services, NJ [RT] 

Les Easter, Tyco/Allied Tube and Conduit, IL [M] 
Rep. National Electrical Manufacturers Association 

Sanford E. Egesdal, Egesdal Associates PLC, MN [M] 
Rep. Automatic Fire Alarm Association, Inc. 



Stanley D. Kahn, Tri-City Electric Company, Inc., CA [IM] 
Rep. National Electrical Contractors Association 

Ray R. Keden, ERICO, Inc., CA [M] 

Rep. Building Industry Consulting Services International 

Juan C. Menendez, Southern California Edison Company, 

CA [UT] 

Rep. Electric Light & Power Group/EEI 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-11 



NATIONAL ELECTRICAL CODE COMMITTEE 



Richard P. Owen, Oakdale, MN [E] 

Rep. International Association of Electrical Inspectors 
Steven J. Owen, Steven J. Owen, Inc., AL [IM] 

Rep. Associated Builders & Contractors 
David A. Pace, Olin Corporation, AL [U] 

Rep. American Chemistry Council 
Melvin K. Sanders, Things Electrical Co., Inc. (TECo., 
Inc.), IA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Mark A. Sepulveda, USA Alarm Systems, Inc., CA [IM] 

Rep. National Burglar & Fire Alarm Association 

(VL to 720, 725, 727, 760) 
John E. Sleights, Travelers Insurance Company, CT [I] 
Susan L. Stene, Underwriters Laboratories Inc., CA [RT] 

Alternates 

Richard S. Anderson, RTKL Associates Inc., VA [M] 

(Alt. to Ray R. Keden) 

Rep. Building Industry Consulting Services International 
Steven D. Burlison, Progress Energy, FL [UT] 

(Alt. to Juan C. Menendez) 

Rep. Electric Light & Power Group/EEI 
Shane M. Clary, Bay Alarm Company, CA [M] 

(Alt. to Sanford E. Egesdal) 

Rep. Automatic Fire Alarm Association, Inc. 
Adam D. Corbin, Corbin Electrical Services, Inc., NJ [IM] 

(Alt. to Lawrence S. Ayer) 

Rep. Independent Electrical Contractors, Inc. 



Danny Liggett, DuPont Company, TX [U] 

(Alt. to David A. Pace) 

Rep. American Chemistry Council 
T. David Mills, Savannah River Nuclear Solutions, LLC, 
SC [U] 

(Alt. to Melvin K. Sanders) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Mark C. Ode, Underwriters Laboratories Inc., AZ [RT] 

(Alt. to Susan L. Stene) 
Roger S. Passmore, IES Industrial, Inc., SC [IM] 

(Alt. to Steven J. Owen) 

Rep. Associated Builders & Contractors 
Marty L. Riesberg, 1BEW Local Union 22, MD [L] 

(Alt. to Paul J. Casparro) 

Rep. International Brotherhood of Electrical Workers 
George A. Straniero, Tyco/ AFC Cable Systems, Inc., 
NJ [M] 

(Alt. to Les Easter) 

Rep. National Electrical Manufacturers Association 
Robert J. Walsh, City of Hayward, CA [E] 

(Alt. to Richard P. Owen) 

Rep. International Association of Electrical Inspectors 
Wendell R. Whistler, Intertek Testing Services, OR [RT] 

(Alt. to Thomas F. Connaughton) 

Nonvoting 

Edward C. Lawry, Oregon, Wl [E] 
(Member Emeritus) 



CODE-MAKING PANEL NO. 4 
Articles 225, 230, 690, 692, 694, 705 

Ronald J. Toomer, Chair 
Toomer Electrical Company Inc., LA [IM] 
Rep. National Electrical Contractors Association 



Ward I. Bower, Sandia National Laboratories, NM [U] 

Rep. Solar Energy Industries Association 

(VL to 690, 692, 705) 
Robert J. Deaton, The Dow Chemical Company, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Tony Dorta, Intertek Testing Services, CA [RT] 
Roger D. McDaniel, Georgia Power Company, GA [UT] 

Rep. Electric Light & Power Group/EEI 
James J. Rogers, Towns of Oak Bluffs, Tisbury, West 
Tisbury, MA [E] 

Rep. International Association of Electrical Inspectors 
John A. Sigmund, PPG Industries, Inc., LA [U] 

Rep. American Chemistry Council 
Todd W. Stafford, National Joint Apprentice & Training 
Committee, TN [L] 

Rep. International Brotherhood of Electrical Workers 
Robert H. Wills, Intergrid, LLC, NH [U] 

Rep. American Wind Energy Association 

(VL to 690, 692, 705) 
John W. Young, Siemens Industry, Inc., GA [M] 

Rep. National Electrical Manufacturers Association 
Timothy P. Zgonena, Underwriters Laboratories Inc., 
IL [RT] 
Vincent C. Zinnante, Westpoint Electric Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 

Alternates 
Paul D. Barnhart, Underwriters Laboratories Inc., NC [RT] 

(Alt. to Timothy P. Zgonena) 
Alex Z. Bradley, The DuPont Company, DE [U] 

(Alt. to John A. Sigmund) 

Rep. American Chemistry Council 



William F. Brooks, Brooks Engineering, CA [U] 

(Alt. to Ward I. Bower) 

Rep. Solar Energy Industries Association 

(VL to 690, 692, 705) 
Thomas E. Bucha), Intertek Testing Services, NY [RT] 

(Alt. to Tony Dorta) 
Larry D. Cogburn, Cogburn Bros, Inc., FL [IM] 

(Alt. to Ronald J. Toomer) 

Rep. National Electrical Contractors Association 
Brian L. Crise, NIETC, OR [L] 

(Alt. to Todd W. Stafford) 

Rep. International Brotherhood of Electrical Workers 
Mark D. Gibbs, B&W Y-12, LLC, TN [U] 

(Alt. to Robert J. Deaton) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Barry N. Hornberger, PECO Energy Company, PA [UT] 

(Alt. to Roger D. McDaniel) 

Rep. Electric Light & Power Group/EEI 
Tim LaLonde, Haskin Electric, Inc., WA [IM] 

(Alt. to Vincent C. Zinnante) 

Rep. Independent Electrical Contractors, Inc. 
Philip M. Piqueira, General Electric Company, CT [Mj 

(Alt. to John W. Young) 

Rep. National Electrical Manufacturers Association 
Robert W. Preus, Abundant Renewable Energy, LLC, 
OR [U] 

(Alt. to Robert H. Wills) 

Rep. American Wind Energy Association 

(VL to 690, 692, 705) 
Glenn A. Soles, Clark County Department of Development 
Services, NV [E] 

(Alt. to James J. Rogers) 

Rep. International Association of Electrical Inspectors 



70-12 



NATIONAL ELECTRICAL CODE 2011 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 5 
Articles 200, 250, 280, 285 

Michael J. Johnston, Chair 
National Electrical Contractors Association, MD [IM] 



Trevor N. Bowmer, Telcordia Technologies, NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 
David Brender, Copper Development Association, Inc., 
NY [M] 

Rep. Copper Development Association Inc. 
Martin J. Brett, Jr., Wheatland Tube Company, DE [M] 

Rep. American Iron and Steel Institute 
Paul Dobrowsky, Innovative Technology Services, NY [U] 

Rep. American Chemistry Council 
Dan Hammel, 1BEW Local Union 704, IA [L] 

Rep. International Brotherhood of Electrical Workers 
G. Scott Harding, F. B. Harding, Inc., MD [IM] 

Rep. Independent Electrical Contractors, Inc. 
William J. Helfrich, US Department of Labor, PA [E] 
Charles F. Mello, Underwriters Laboratories Inc., WA [RT] 
Daleep C. Mohla, DCM Electrical Consulting Services, Inc., 
TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Christine T. Porter, Intertek Testing Services, WA [RT] 
Gregory J. Steinman, Thomas & Betts Corporation, TN [M] 

Rep. National Electrical Manufacturers Association 
Robert G. Stoll, Thomas Associates, Inc., OH [M] 

Rep. Power Tool Institute, Inc 
Richard Temblador, Southwire Company, GA [M] 

Rep. The Aluminum Association, Inc. 
C. Douglas White, CenterPoint Energy, Inc., TX [UT] 

Rep. Electric Light & Power Group/EEI 
David A. Williams, Delta Charter Township, MI [E] 

Rep. International Association of Electrical Inspectors 

Alternates 

Ron D. Alley, Northern New Mexico 1EC, NM [IM] 

(Alt. to G. Scott Harding) 

Rep. Independent Electrical Contractors, Inc. 
Joseph P. DeGregoria, Underwriters Laboratories Inc., 
NY [RT] 

(Alt. to Charles F. Mello) 
Ronald Lai, Burndy LLC, NH [M] 

(Alt. to Gregory J. Steinman) 

Rep. National Electrical Manufacturers Association 



Paul J. LeVasseur, Bay City JEATC, MI [L] 

(Alt. to Dan Hammel) 

Rep. International Brotherhood of Electrical Workers 
Richard E. Loyd, R & N Associates, AZ [M] 

(Alt. to Martin J. Brett, Ir.) 

Rep. American Iron and Steel Institute 
Randall R. McCarver, Telcordia Technologies, Inc., NJ [U] 

(Alt. to Trevor N. Bowmer) 

Rep. Alliance for Telecommunications Industry Solutions 
Michael E. McNeil, FMC Bio Polymer, ME [U] 

(Alt. to Paul Dobrowsky) 

Rep. American Chemistry Council 
Mike O'Meara, Arizona Public Service Company, AZ [UT] 

(Alt. to C. Douglas White) 

Rep. Electric Light & Power Group/EEI 
William A. Pancake, III, Universal Engineering Sciences, 
FL [E] 

(Alt. to David A. Williams) 

Rep. International Association of Electrical Inspectors 
Nathan Philips, Integrated Electronic Systems, OR [IM] 

(Alt. to Michael J. Johnston) 
Paul R. Picard, Tyco/AFC Cable Systems, Inc., MA [M] 

(Alt. to Richard Temblador) 

Rep. The Aluminum Association, Inc. 
Elliot Rappaport, Electro Technology Consultants, Inc., FL [U] 

(Alt. to Daleep C. Mohla) 

Rep. Institute of Electrical '& Electronics Engineers, Inc. 
Phil Simmons, Simmons Electrical Services, WA [M] 

(Alt. to David Brender) 

Rep. Copper Development Association Inc. 
Thomas R. Siwek, Robert Bosch Tool Corporation, IL [M] 

(Alt. to Robert G. Stoll) 

Rep. Power Tool Institute, Inc. 

Nonvoting 

Robert A. Nelson, Canadian Standards Association, 
Canada [RT] 



CODE-MAKING PANEL NO. 6 
Articles 310, 400, 402, Chapter 9 Tables 5 through 9, and Annex B 

Scott Cline, Chair 
McMurtrey Electric, Inc., CA [IM] 
Rep. National Electrical Contractors Association 



Samuel B. Friedman, General Cable Corporation, RI [M] 

Rep. National Electrical Manufacturers Association 
Robert L. Huddleston, Jr., Eastman Chemical Company. 
TN [U] 

Rep. American Chemistry Council 
Randal Hunter, City of Las Vegas, NV [E] 

Rep. International Association of Electrical Inspectors 
G. W. Kent, Kent Electric & Plumbing Systems, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
William F. Laidler, IBEW Local 223 JATC, MA [L] 

Rep. International Brotherhood of Electrical Workers 
L. Bruce McClung, Mc Squared Electrical Consulting LLC, 
WV [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Paul R. Picard, Tyco/AFC Cable Systems, Inc., MA [M] 

Rep. The Aluminum Association, Inc. 
John M. Thompson, Underwriters Laboratories Inc., NC [RT] 



Carl Timothy Wall, Alabama Power Company, AL [UT] 

Rep. Electric Light & Power Group/EEI 
Joseph S. Zimnoch, The Okonite Company, NJ [M] 

Rep. Copper Development Association Inc. 

Alternates 
Peter E. Bowers, Satellite Electric Company, Inc., MD [IM] 

(Alt. to G. W. Kent) 

Rep. Independent Electrical Contractors, Inc. 
John J. Cangemi, Underwriters Laboratories Inc., NY [RT] 

(Alt. to John M. Thompson) 
James M. Daly, General Cable, NJ [M] 

(Alt. to Joseph S. Zimnoch) 

Rep. Copper Development Association Inc. 
Roland E. Deike, CenterPoint Energy, Inc., TX [UT] 

(Alt. to Carl Timothy Wall) 

Rep. Electric Light & Power Group/EEI 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-13 



NATIONAL ELECTRICAL CODE COMMITTEE 



Richard A. Holub, DuPont Engineering, DE [U] 

(Alt. to Robert L. Huddleston, Jr.) 

Rep. American Chemistry Council 
Phillip J. Huff, Inglett & Stubbs LLC, GA [IM] 

(Alt. to Scott Cline) 

Rep. National Electrical Contractors Association 
Christel K. Hunter, Alcan Cable, NV [M] 

(Alt. to Paul R. Picard) 

Rep. The Aluminum Association, Inc. 
Lowell Lisker, American Insulated Wire Corporation, MA [M] 

(Alt. to Samuel B. Friedman) 

Rep. National Electrical Manufacturers Association 



John Stacey, City of St. Louis, MO [E] 

(Alt. to Randal Hunter) 

Rep. International Association of Electrical Inspectors 
Donald A. Voltz, BP, TX [U] 

(Alt. to L. Bruce McClung) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
James R. Weimer, Eastern Idaho Electrical JATC, ID [LI 

(Alt. to William F. Laidler) 

Rep. International Brotherhood of Electrical Workers 



CODE-MAKING PANEL NO. 7 
Articles 320, 322, 324, 326, 328, 330, 332, 334, 336, 338, 340, 382, 394, 396, 398, 399 

Michael W. Smith, Chair 
Wentzel Electric, MO [IM] 
Rep. National Electrical Contractors Association 



Thomas H. Cybula, Underwriters Laboratories Inc., 

NY [RT] 

James M. Daly, General Cable, NJ [M] 

Rep. National Electrical Manufacturers Association 
Chris J. Fahrenthold, Facilities Solutions Group, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Herman J. Hall, Austin, TX [M] 

Rep. The Vinyl Institute 
James K. Hinrichs, State of Washington, WA [E] 

Rep. International Association of Electrical Inspectors 
Christel K. Hunter, Alcan Cable, NV [M] 

Rep. The Aluminum Association, Inc. 
Samuel R. La Dart, City of Memphis, TN [L] 

Rep. International Brotherhood of Electrical Workers 
Ronald G. Nickson, National Multi Housing Council, DC [U] 
Dennis A. Nielsen, Lawrence Berkeley National Laboratory, 
CA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
John W. Ray, Duke Energy Corporation, NC [UT] 

Rep. Electric Light & Power Group/EEI 
Gregory L. Runyon, Eli Lilly and Company, IN [U] 

Rep. American Chemistry Council 
David E. Schumacher, Associated Builders and Contractors, 
I A [IM] 

Rep. Associated Builders & Contractors 
George A. Straniero, Tyco/AFC Cable Systems, Inc., NJ [M] 

Rep. Copper Development Association Inc. 



Alternates 
William B. Crist, Houston Stafford Electric Company, TX [IM] 

(Alt. to Chris J. Fahrenthold) 

Rep. Independent Electrical Contractors, Inc. 
Donald G. Dunn, Aramco Services Company, TX [U] 

(Alt. to Dennis A. Nielsen) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Rachel E. Krepps, Baltimore Gas & Electric Company, 
MD [UT] 

(Alt. to John W. Ray) 

Rep. Electric Light & Power Group/EEI 
Charles David Mercier, Southwire Company, GA [M] 

(Alt. to James M. Daly) 

Rep. National Electrical Manufacturers Association 
Keith Owensby, Chattanooga Electrical JATC, TN [L] 

(Alt. to Samuel R. La Dart) 

Rep. International Brotherhood of Electrical Workers 
Charles J. Palmieri, Town of Norwell, MA [E] 

(Alt. to James K. Hinrichs) 

Rep. International Association of Electrical Inspectors 
Kevin T. Porter, Encore Wire Corporation, TX [M] 

(Alt. to George A. Straniero) 

Rep. Copper Development Association Inc. 
Susan L. Stene, Underwriters Laboratories Inc., CA [RT] 

(Alt. to Thomas H. Cybula) 
Peter Waldrab, Alcan Cable, PA [M] 

(Alt. to Christel K. Hunter) 

Rep. The Aluminum Association, Inc. 
Wesley L. Wheeler, Cogburn Bros., Inc., FL [IM] 

(Alt. to Michael W. Smith) 

Rep. National Electrical Contractors Association 



CODE-MAKING PANEL NO. 8 

Articles 342, 344, 348, 350, 352, 353, 354, 355, 356, 358, 360, 362, 366, 368, 370, 372, 374, 376, 378, 380, 
384, 386, 388, 390, 392, Chapter 9, Tables 1 through 4, and Annex C 

Julian R. Burns, Chair 
Quality Power Solutions, Inc., NC [IM] 
Rep. Independent Electrical Contractors, Inc. 



Joyce Evans Blom, The Dow Chemical Company, CA [U] 

Rep. American Chemistry Council 
David M. Campbell, Tyco/AFC Cable Systems, Inc., MA [M] 

Rep. The Aluminum Association, Inc. 
Joseph Dabe, City of St. Paul, MN [L] 

Rep. International Brotherhood of Electrical Workers 
M. Shan Griffith, Elektek, PLLC, TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David G. Humphrey, County of Henrico, Virginia, VA [E] 

Rep. International Association of Electrical Inspectors 



David H. Kendall, Thomas & Betts Corporation, OH [M] 

Rep. The Vinyl Institute 
Richard E. Loyd, R & N Associates, AZ [M] 

Rep. American Iron and Steel Institute 
Stephen P. Poholski, Newkirk Electric Associates, Inc., MI [IM] 

Rep. National Electrical Contractors Association 
George F. Walbrecht, Underwriters Laboratories Inc., IL [RT] 
Rodney J. West, Square D Company/Schneider Electric, OH |MJ 

Rep. National Electrical Manufacturers Association 
Leslie R. Zielke, South Carolina Electric & Gas Company, 
SC [UT] 

Rep. Electric Light & Power Group/EEI 



70-14 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Alternates 
Richard J. Herman, Underwriters Laboratories Inc., IL [RT] 

(Alt. to George F. Walbrecht) 
Duane A. Carlson, PRS Consulting Engineers, WA [U] 

(Alt. to M. Shan Griffith) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
George R. Dauberger, Thomas & Betts Corporation, TN [M] 

(Alt. to David H. Kendall) 

Rep. The Vinyl Institute 
James T. Dwight, Sasol North America, Inc., LA [U] 

(Alt. to Joyce Evans Blom) 

Rep. American Chemistry Council 
Kenneth J. Gilbert, Florida Power & Light Company, FL [UT] 

(Alt. to Leslie R. Zielke) 

Rep. Electric Light & Power Group/EEI 
Kenneth W. Hengst, EAS Contracting, LP, TX [IM] 

(Alt. to Julian R. Burns) 

Rep. Independent Electrical Contractors, Inc. 



James M. Imlah, City of Hillsboro, OR [E] 

(Alt. to David G. Humphrey) 

Rep. International Association of Electrical Inspectors 
Gregory L. Maurer, Wheatland Tube Company, PA [M] 

(Alt. to Richard E. Loyd) 

Rep. American Iron and Steel Institute 
Gary W. Pemble, Montana Electrical JATC, MT [L] 

(Alt. to Joseph Dabe) 

Rep. International Brotherhood of Electrical Workers 
Frederic F. Small, Hubbell Incorporated, CT [M] 

(Alt. to Rodney J. West) 

Rep. National Electrical Manufacturers Association 
Richard Temblador, Southwire Company, GA [M] 

(Alt. to David M. Campbell) 

Rep. The Aluminum Association, Inc. 



CODE-MAKING PANEL NO. 9 
Articles 312, 314, 404, 408, 450, 490 

Robert A. McCullough, Chair 
Tuckerton, NJ [E] 
Rep. International Association of Electrical Inspectors 



Rodney D. Belisle, NECA-IBEW Electrical Training Trust, 
OR[L] 

Rep. International Brotherhood of Electrical Workers 
Billy Breitkreutz, Fluor Corporation, TX [U] 

Rep. Associated Builders & Contractors 
Paul D. Coghill, Intertek Testing Services, OH [RT] 
Richard P. Fogarty, Consolidated Edison Company of New 
York, Inc., NY [UT] 

Rep. Electric Light & Power Group/EEI 
Frederic P. Hartwell, Hartwell Electrical Services, Inc., 
MA [SE] 
Thomas J. LeMay, LeMay Electric, Inc., GA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Robert D. Osborne, Underwriters Laboratories Inc., 
NC [RT] 
Bradford D. Rupp, Allied Moulded Products, Inc., OH [M] 

Rep. National Electrical Manufacturers Association 
Sukanta Sengupta, FMC Corporation, NJ [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Monte Szendre, Wilson Construction Company, OR [IM] 

Rep. National Electrical Contractors Association 
Ralph H. Young, Eastman Chemical Company, TN [U] 

Rep. American Chemistry Council 



Alternates 



Kevin J. Breen, Breen Electrical Contractors Inc., NY [IM] 

(Alt. to Thomas J. LeMay) 

Rep. Independent Electrical Contractors, Inc. 
Robert R. Gage, National Grid, NY [UT] 

(Alt. to Richard P. Fogarty) 

Rep. Electric Light & Power Group/EEI 
L. Keith Lofland, International Association of Electrical 
Inspectors (IAEI), TX [E] 

(Alt. to Robert A. McCullough) 
Kenneth L. McKinney, Jr., Underwriters Laboratories Inc., 
NC [RT] 

(Alt. to Robert D. Osborne) 
Paul W. Myers, Potash Corporation, OH [U] 

(Alt. to Sukanta Sengupta) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Ronnie H. Ridgeway, Siemens Industry, Inc., TX [M] 

(Alt. to Bradford D. Rupp) 

Rep. National Electrical Manufacturers Association 
Rhett A. Roe, IBEW Local Union 26 JATC, MD [L] 

(Alt. to Rodney D. Belisle) 

Rep. International Brotherhood of Electrical Workers 



CODE-MAKING PANEL NO. 10 

Article 240 

Donald R. Cook, Chair 
Shelby County Development Services, AL [E] 
Rep. International Association of Electrical Inspectors 



Madeline Borthick, IEC of Houston, Inc., TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Dennis M. Darling, Stantec, Canada [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
James T. Dollard, Jr., IBEW Local Union 98, PA [L] 

Rep. International Brotherhood of Electrical Workers 
Charles Eldridge, Indianapolis Power & Light Company, IN 
[UT] 

Rep. Electric Light & Power Group/EEI 
Carl Fredericks, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 
Roderic Hageman, PRIT Service, Inc., IL [IM] 

Rep. InterNational Electrical Testing Association 



Jeffrey H. Hidaka, Underwriters Laboratories Inc., IL [RT] 
Alan Manche, Square D Company/Schneider Electric, KY [M] 

Rep. National Electrical Manufacturers Association 
Robert W. Mount, Jr., Hussmann Corporation, MO [M] 

Rep. Air-Conditioning, Heating, & Refrigeration Institute 
George J. Ockuly, Technical Marketing Consultants, MO [M] 
Richard Sobel, Quantum Electric Corporation, NY [IM] 

Rep. National Electrical Contractors Association 

Alternates 
Scott A. Blizard, American Electrical Testing Company, 
Inc., MA [IM] 

(Alt. to Roderic Hageman) 

Rep. Internationa] Electrical Testing Association 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-15 



NATIONAL ELECTRICAL CODE COMMITTEE 



Robert J. Kauer, Building Inspection Underwriters, Inc., 
PA [E] 

(Alt. to Donald R. Cook) 

Rep. International Association of Electrical Inspectors 
Frank G. Ladonne, Underwriters Laboratories Inc., IL [RT] 

(Alt. to Jeffrey H. Hidaka) 
Kevin J. Lippert, Eaton Corporation, PA [M] 

(Alt. to Alan Manche) 

Rep. National Electrical Manufacturers Association 
Richard E. Lofton, II, IBEW Local Union 280, OR [L] 

(Alt. to James T. Dollard, Jr.) 

Rep. International Brotherhood of Electrical Workers 
Vincent J. Saporita, Cooper Bussmann, MO [M] 

(Alt. to George J. Ockuly) 



Roy K. Sparks, III, Eli Lilly and Company, IN [U] 

(Alt. to Carl Fredericks) 

Rep. American Chemistry Council 
Steve A. Struble, Freeman's Electric Service, Inc., SD [IM] 

(Alt. to Madeline Borthick) 

Rep. Independent Electrical Contractors, Inc. 
Steven E. Townsend, General Motors Corporation, MI [U] 

(Alt. to Dennis M. Darling) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
John F. Vartanian, National Grid, MA [UT] 

(Alt. to Charles Eldridge) 

Rep. Electric Light & Power Group/EEI 



CODE-MAKING PANEL NO. 11 
Articles 409, 430, 440, 460, 470, Annex D, Example D8 

Wayne Brinkmeyer, Chair 
Britain Electric Company, TX [IM] 
Rep. National Electrical Contractors Association 



Terry D. Cole, Hamer Electric, Inc., WA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Jeffrey A. Desjarlais, Underwriters Laboratories Inc., IL [RT] 
James M. Fahey, IBEW Local Union 103/MBTA, MA [L] 

Rep. International Brotherhood of Electrical Workers 
Robert G. Fahey, City of Janesville, WI [E] 

Rep. International Association of Electrical Inspectors 
William D. Glover, PPG Industries, Inc., WV [U] 

Rep. American Chemistry Council 
Paul E. Guidry, Fluor Enterprises, Inc., TX [U] 

Rep. Associated Builders & Contractors 
Paul S. Hamer, Chevron Energy Technology Company, CA [U] 

Rep. American Petroleum Institute 
James C. Missildine, Jr., Southern Company Services, Inc., 
AL [UT] 

Rep. Electric Light & Power Group/EEI 
Vincent J. Saporita, Cooper Bussmann, MO [M] 
Lynn F. Saunders, Brighton, MI [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Lawrence E. Todd, Intertek Testing Services, OR [RT] 
Ron Widup, Shermco Industries, Inc., TX [IM] 

Rep. InterNational Electrical Testing Association 
James R. Wright, Siemens Industry, Inc., IL [M] 

Rep. National Electrical Manufacturers Association 

Alternates 
Stanley J. Folz, Morse Electric Company, NV [IM] 

(Alt. to Wayne Brinkmeyer) 

Rep. National Electrical Contractors Association 
Philip C. Hack, Constellation Energy Power Generation, 
MD [UT] 

(Alt. to James C. Missildine, Jr.) 

Rep. Electric Light & Power Group/EEI 



Barry G. Karnes, Underwriters Laboratories Inc., CA [RT] 

(Alt. to Jeffrey A. DesJarlais) 
Ed Larsen, Square D Company/Schneider Electric, IA [M] 

(Alt. to James R. Wright) 

Rep. National Electrical Manufacturers Association 
Thomas E. Moore, City of Beachwood, OH [E] 

(Alt. to Robert G. Fahey) 

Rep. International Association of Electrical Inspectors 
Arthur S. Neubauer, Arseal Technologies, GA [U] 

(Alt. to Paul S. Hamer) 

Rep. American Petroleum Institute 
Jebediah J. Novak, Cedar Rapids Electrical JATC, IA [L] 

(Alt. to James M. Fahey) 

Rep. International Brotherhood of Electrical Workers 
George J. Ockuly, Technical Marketing Consultants, MO [M] 

(Alt. to Vincent J. Saporita) 
Charles L. Powell, Eastman Chemical Company, TN [U] 

(Alt. to William D. Glover) 

Rep. American Chemistry Council 
Arthur J. Smith, III, Waldemar S. Nelson & Company. 
Inc., LA [U] 

(Alt. to Lynn F. Saunders) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
L. Matthew Snyder, Intertek Testing Services, NY [RT] 

(Alt. to Lawrence E. Todd) 
Russell A. Tiffany, R. A. Tiffany & Associates, PA [M] 

(Voting Alt. to AHRI Rep.) 

Rep. Air-Conditioning, Heating, & Refrigeration Institute 
Michael K. Weitzel, Central Washington Electrical 
Education, WA [IM] 

(Alt. to Terry D. Cole) 

Rep. Independent Electrical Contractors, Inc. 



CODE-MAKING PANEL NO. 12 

Articles 610, 620, 625, 626, 630, 640, 645, 647, 650, 660, 665, 668, 669, 670, 685, 

Annex D, Examples D9 and D10 

Timothy M. Croushore, Chair 
Allegheny Power, PA [UT] 
Rep. Electric Light & Power Group/EEI 



William E. Anderson, The Procter & Gamble Company, OH [U] 
Rep. Institute of Electrical & Electronics Engineers, Inc. 

Thomas R. Brown, Intertek Testing Services, NY [RT] 

Karl M. Cunningham, Alcoa, Inc., PA [M] 
Rep. The Aluminum Association, Inc. 
(VL to 610, 625, 630, 645, 660, 665, 668, 669, 685) 



Thomas L. Hedges, Hedges Electric & Construction Inc., 
CA [IM] 

Rep. National Electrical Contractors Association 
Michael J. Hittel, GM Worldwide Facilities Group, MI [U] 

Rep. Society of Automotive Engineers-Hybrid Committee 



70- 



NATIONAL ELECTRICAL CODE 201 1 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Robert E. Johnson, ITE Safety, MA [U] 

Rep. Information Technology Industry Council 

(VL to 640, 645, 647, 685) 
Andy Juhasz, Kone, Inc., IL [M] 

Rep. National Elevator Industry Inc. 

(VLto610, 620, 630) 
Stanley Kaufman, CableSafe, Inc./OFS, GA [M] 

Rep. Society of the Plastics Industry, Inc. 

(VL to 640, 645) 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 
Todd Lottmann, Cooper Bussmann, MO [M] 

Rep. National Electrical Manufacturers Association 
Sam Marcovici, New York City Department of Buildings, 
NY [E] 
Tim McClintock, Wayne County, Ohio, OH [E] 

Rep. International Association of Electrical Inspectors 
David R. Quave, IBEW Local Union 903, MS [L] 

Rep. International Brotherhood of Electrical Workers 
Duke W. Schamel, Electrical Service Solutions, Inc., CO [IM] 

Rep. Independent Electrical Contractors, Inc. 
Arthur E. Schlueter, Jr., A. E. Schlueter Pipe Organ 
Company, GA [M] 

Rep. American Institute of Organ Builders 

(VL to 640, 650) 
Robert C. Turner, Inductotherm Corporation, MD [M] 

(VL to 610, 630, 665, 668, 669) 
Ryan Gregory Ward, IdleAire, Inc., TN [U] 

Rep. Transportation Electrification Committee 

(VL to 625, 626) 
Kenneth White, Olin Corporation, NY [U] 

Rep. American Chemistry Council 

Alternates 
Timothy M. Andrea, Southwire Company, GA [M] 
(Alt. to Karl M. Cunningham) 
Rep. The Aluminum Association, Inc. 
(VL to 610, 625, 630, 645, 660, 665, 668, 669, 685) 



Jeffrey W. Blain, Schindler Elevator Corporation, NY [M] 

(Alt. to Andy Juhasz) 

Rep. National Elevator Industry Inc. 

(VL to 610, 620, 630) 
Thomas M. Burke, Underwriters Laboratories Inc., CA [RT] 

(Alt. to John R. Kovacik) 
Jeffrey L. Holmes, IBEW Local Union 1 JATC, MO [L] 

(Alt. to David R. Quave) 

Rep. International Brotherhood of Electrical Workers 
Gery J. Kissel, General Motors Corporation, MI [U] 

(Alt. to Michael J. Hittel) 

Rep. Society of Automotive Engineers-Hybrid Committee 
Todd R. Konieczny, Intertek Testing Services, MA [RT] 

(Alt. to Thomas R. Brown) 
Christopher P. O'Neil, NSTAR Electric & Gas Corporation, 
MA [UT] 

(Alt. to Timothy M. Croushore) 

Rep. Electric Light & Power Group/EEI 
David L. Sher, City of Bellevue, WA [E] 

(Alt. to Tim McClintock) 

Rep. International Association of Electrical Inspectors 
Emad Tabatabaei, Inductotherm Corporation, NJ [M] 

(Alt. to Robert C. Turner) 

(VL to 610, 630, 665, 668, 669) 
Lori L. Tennant, Square D Company/Schneider Electric, NC [M] 

(Alt. to Todd Lottmann) 

Rep. National Electrical Manufacturers Association 
Stephen J. Thorwegen, Jr., FSG Electric, TX [IM] 

(Alt. to Duke W. Schamel) 

Rep. Independent Electrical Contractors, Inc. 
Charles M. Trout, Maron Electric Company, FL [IM] 

(Alt. to Thomas L. Hedges) 

Rep. National Electrical Contractors Association 

Nonvoting 

Andre R. Cartal, Yardley, PA [E] 
(Member Emeritus) 



CODE-MAKING PANEL NO. 13 
Articles 445, 455, 480, 695, 700, 701, 702, 708, Annex F, and Annex G 

Donald P. Bliss, Chair 
NI2 Center for Infrastructure Expertise, NH [U] 



Martin D. Adams, Adams Electric, Inc., CO [IM] 

Rep. National Electrical Contractors Association 
Suzanne M. Borek, New Jersey Department of Community 
Affairs, NJ [E] 

Rep. International Association of Electrical Inspectors 
James L. Brown, Detroit Edison, DTE Energy, MI [UT] 

Rep. Electric Light & Power Group/EEI 
Daniel J. Caron, Bard, Rao + Athanas Consulting 
Engineers, LLC, MA [SE] 
James S. Conrad, Tyco Thermal Controls, CT [M] 

Rep. Copper Development Association Inc. 
Richard D. Currin, Jr., North Carolina State University, 
NC [U] 

Rep. American Society of Agricultural & Biological 

Engineers 
Neil A. Czarnecki, Reliance Controls Corporation, WI [M] 

Rep. National Electrical Manufacturers Association 
Herbert H. Daugherty, Electric Generating Systems 
Association, NJ [M] 
James E. Degnan, Sparling, WA [U] 

Rep. American Society for Healthcare Engineering 
Ronald A. Keenan, M. C. Dean, Inc., VA [IM] 

Rep. Independent Electrical Contractors, Inc. 
Linda J. Little, IBEW Local 1 Electricians JATC, MO [L] 

Rep. International Brotherhood of Electrical Workers 
Craig A. Mouton, ExxonMobil Chemical Corporation, TX [U] 

Rep. American Chemistry Council 



Mark C. Ode, Underwriters Laboratories Inc., AZ [RT] 
Gary L. Olson, Cummins Power Generation, MN [M] 
Michael L. Savage, Sr., Middle Department Inspection 
Agency, Inc., MD [E] 
Mario C. Spina, Verizon Wireless, OH [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
David Tobias, Jr., Intertek Testing Services, OH [RT] 

Alternates 
Barry S. Bauman, Alliant Energy, WI [U] 

(Alt. to Richard D. Currin, Jr.) 

Rep. American Society of Agricultural & Biological 

Engineers 
Steven A. Corbin, Corbin Solar Solutions LLC, NJ [IM] 

(Alt. to Ronald A. Keenan) 

Rep. Independent Electrical Contractors, Inc. 
James T. Dollard, Jr., IBEW Local Union 98, PA [L] 

(Alt. to Linda J. Little) 

Rep. International Brotherhood of Electrical Workers 
Lawrence W. Forshner, Cummins Northeast, Inc., MA [M] 

(Alt. to Gary L. Olson) 
Chad Kennedy, Square D Company/Schneider Electric, SC [M] 

(Alt. to Neil A. Czarnecki) 

Rep. National Electrical Manufacturers Association 
John R. Kovacik, Underwriters Laboratories Inc., IL [RT] 

(Alt. to Mark C. Ode) 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-17 



NATIONAL ELECTRICAL CODE COMMITTEE 



Peter M. Olney, Vermont Department of Public Safety, VT [E] 

(Alt. to Suzanne M. Borek) 

Rep. International Association of Electrical Inspectors 
Bayly Morgan Tyler, Consolidated Edison Company of New 
York Inc., NY [UT] 

(Alt. to James L. Brown) 

Rep. Electric Light & Power Group/EEI 



Herbert V. Whittall, Electrical Generating Systems 
Association, FL [M] 

(Alt. to Herbert H. Daugherty) 



CODE-MAKING PANEL NO. 14 

Articles 500, 501, 502, 503, 504, 505, 506, 510, 511, 513, 514, 515, and 516 

Robert A. Jones, Chair 
Independent Electrical Contractors, Inc., TX [IM] 
Rep. Independent Electrical Contractors, Inc. 



Daniel Batta, Jr., Constellation Power Source Generation, 
Inc., MD [UT] 

Rep. Electric Light & Power Group/EEI 
Marc J. Bernsen, National Electrical Contractors 
Association, ID [IM] 

Rep. National Electrical Contractors Association 
Edward M. Briesch, Underwriters Laboratories Inc., IL [RT] 
James D. Cospolich, Waldemar S. Nelson & Company Inc., 
LA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Mark Goodman, Jacobs Engineering Group, CA [U] 

Rep. American Petroleum Institute 
Joseph H. Kuczka, Killark Electric Manufacturing 
Company, MO [M] 

Rep. National Electrical Manufacturers Association 
William G. Lawrence, Jr., FM Global, MA [I] 
L. Evans Massey, Baldor Electric Company, SC [M] 

Rep. Instrumentation, Systems, & Automation Society 
Jeremy Neagle, Intertek Testing Services, NY [RT] 
Donald R. Offerdahl, North Dakota State Electrical Board, 
ND [E] 

Rep. International Association of Electrical Inspectors 
John L. Simmons, Florida East Coast JATC, FL [L] 

Rep. International Brotherhood of Electrical Workers 
David B. Wechsler, The Dow Chemical Company, TX [U] 

Rep. American Chemistry Council 
Mark C. Wirfs, R & W Engineering, Inc., OR [U] 

Rep. Grain Elevator and Processing Society 

Alternates 

Harold G. Alexander, American Electric Power Company, 
OH [UT] 

(Alt. to Daniel Batta, Jr.) 

Rep. Electric Light & Power Group/EEI 
Donald W. Ankele, Underwriters Laboratories Inc., IL [RT] 

(Alt. to Edward M. Briesch) 



Steven J. Blais, EGS Electrical Group, IL [M] 

(Alt. to Joseph H. Kuczka) 

Rep. National Electrical Manufacturers Association 
Mark W. Bonk, Cargill Incorporated, MN [U] 

(Alt. to Mark C. Wirfs) 

Rep. Grain Elevator and Processing Society 
Dave Burns, Shell Exploration & Production Company, 
TX [U] 

(Alt. to Mark Goodman) 

Rep. American Petroleum Institute 
Larry W. Burns, Burns Electric, Inc., TX [IM] 

(Alt. to Robert A. Jones) 

Rep. Independent Electrical Contractors, Inc. 
Jonathan L. Cadd, International Association of Electrical 
Inspectors, TX [E] 

(Alt. to Donald R. Offerdahl) 
Thomas E. Dunne, Long Island Joint Apprenticeship 
& Training Committee, NY [L] 

(Alt. to John L. Simmons) 

Rep. International Brotherhood of Electrical Workers 
Richard A. Holub, DuPont Engineering, DE [U] 

(Alt. to David B. Wechsler) 

Rep. American Chemistry Council 
Ted H. Schnaare, Rosemount Incorporated, MN [M] 

(Alt. to L. Evans Massey) 

Rep. Instrumentation, Systems, & Automation Society 
Donald W. Zipse, Zipse Electrical Forensics, LLC, PA [U] 

(Alt. to James D. Cospolich) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 

Nonvoting 

Timothy J. Pope, Canadian Standards Association, 
Canada [RT] 

Eduardo N. Solano, Estudio Ingeniero Solano S.A., 
Argentina [SE] 

Fred K. Walker, US Department of the Air Force, FL [U] 
Rep. TC on Airport Facilities 



CODE-MAKING PANEL NO. 15 

Articles 517, 518, 520, 522, 525, 530, 540 

Donald J. Talka, Chair 
Underwriters Laboratories Inc., NY [RT] 



James R. Duncan, Sparling Electrical Engineering 
& Technology Consulting, WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Ronald E. Duren, PacifiCorp, WA [UT] 

Rep. Electric Light & Power Group/EEI 
Douglas S. Erickson, American Society for Healthcare 
Engineering, VI [U] 

Rep. American Society for Healthcare Engineering 
Mitchell K. Hefter, Entertainment Technology/Philips, 
TX [IM] 

Rep. Illuminating Engineering Society of North America 

(VL to 518, 520, 525, 530, 540) 



Kim Jones, Funtastic Shows, OR [U] 

Rep. Outdoor Amusement Business Association. Inc. 

(VL to 525) 
Edwin S. Kramer, Radio City Music Hall, NY [L] 

Rep. International Alliance of Theatrical Stage Employees 

(VL to 518, 520, 525, 530, 540) 
Larry Lau, US Department of Veterans Affairs, DC [U] 

(VLto517, 518) 
Stephen M. Lipster, The Electrical Trades Center, OH [L] 

Rep. International Brotherhood of Electrical Workers 
Hugh O. Nash, Jr., Nash Lipsey Burch, LLC, TN [SE] 

Rep. TC on Electrical Systems 



70- 



NATIONAL ELECTRICAL CODE 201 1 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



Kevin T. Porter, Encore Wire Corporation, TX [M] 

Rep. The Aluminum Association, Inc. 
Marcus R. Sampson, Minnesota Department of Labor 
& Industry, MN [E] 

Rep. Internationa] Association of Electrical Inspectors 
James C. Seabury III, Enterprise Electric, LLC, TN [IM] 

Rep. Independent Electrical Contractors, Inc. 
Bruce D. Shelly, Shelly Electric Company, Inc., PA [IM] 

Rep. National Electrical Contractors Association 
Michael D. Skinner, CBS Studio Center, CA [U] 

Rep. Alliance of Motion Picture and Television Producers 

(VLto 518, 520, 525, 530, 540) 
Kenneth E. Vannice, Leviton Manufacturing Company Inc., 
OR [M] 

Rep. US Institute for Theatre Technology 

(VL to 518, 520, 525, 530, 540) 
Michael Velvikis, High Voltage Maintenance Corporation, 
Wl [IM] 

Rep. InterNational Electrical Testing Association 
James L. Wiseman, Square D Company/Schneider Electric, 
TN [M] 

Rep. National Electrical Manufacturers Association 

Alternates 

Gary A. Beckstrand, Utah Electrical JATC, UT [L] 
(Alt. to Stephen M. Lipster) 
Rep. International Brotherhood of Electrical Workers 



James L. Brown, Detroit Edison, DTE Energy, MI [UT] 

(Alt. to Ronald E. Duren) 

Rep. Electric Light & Power Group/EEI 
Matthew B. Dozier, IDesign Services, TN [U] 

(Alt. to James R. Duncan) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Samuel B. Friedman, General Cable Corporation, RI [M] 

(Alt. to James L. Wiseman) 

Rep. National Electrical Manufacturers Association 
Steven R. Goodman, Alcan Cable, PA [M] 

(Alt. to Kevin T. Porter) 

Rep. The Aluminum Association, Inc. 
Dennis W. Marshall, D & L Electric Company, TX [IM] 

(Alt. to James C. Seabury III) 

Rep. Independent Electrical Contractors, Inc. 
Joseph P. Murnane, Jr., Underwriters Laboratories Inc., 
NY [RT] 

(Alt. to Donald J. Talka) 
Richard E. Pokorny, City of Marshfield, Wisconsin, WI [E] 

(Alt. to Marcus R. Sampson) 

Rep. International Association of Electrical Inspectors 
Steven R. Terry, Electronic Theatre Controls Inc., NY [M] 

(Alt. to Kenneth E. Vannice) 

Rep. US Institute for Theatre Technology 

(VL to 5 1 8, 520, 525, 530, 540) 



CODE-MAKING PANEL NO. 16 
Articles 770, 800, 810, 820, 830, 840 

Ron L. Janikowski, Chair 
City of Wausau, Wisconsin, Wl [E] 
Rep. International Association of Electrical Inspectors 



Donna Ballast, dbi, TX [M] 

Rep. Telecommunications Industry Association 
George Bish, MasTec, Inc., dba Advanced Technologies, NC [IM] 

Rep. Satellite Broadcasting & Communications 

Association 
J. Robert Boyer, GE Security, NJ [M] 

Rep. National Electrical Manufacturers Association 
James E. Brunssen, Telcordia, NJ [U] 

Rep. Alliance for Telecommunications Industry Solutions 
Gerald Lee Dorna, Belden Wire & Cable Co., IN [M] 

Rep. Insulated Cable Engineers Association Inc. 
Ralph M. Esemplare, Consolidated Edison Company of 
New York, NY [UT] 

Rep. Electric Light & Power Group/EEI 
Dale R. Funke, Shell Oil Company, TX [U] 

Rep. American Chemistry Council 
Roland W. Gubisch, Intertek Testing Services, MA [RT] 
Randolph J. Ivans, Underwriters Laboratories Inc., NY [RT] 
Robert W. Jensen, dbi-Telecommunication Infrastructure 
Design, TX [M] 

Rep. Building Industry Consulting Services Internationa] 
Steven C. Johnson, Johnson Telecom, LLC, NC [UT] 

Rep. National Cable & Telecommunications Association 
William J. McCoy, Telco Sales, Inc., TX [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Harold C. Ohde, IBEW-NECA Technical Institute, IL [L] 

Rep. International Brotherhood of Electrical Workers 
W. Douglas Pirkle, Pirkle Electric Company, Inc., GA [IM] 

Rep. National Electrical Contractors Association 
Luigi G. Prezioso, M. C. Dean, Inc., VA [IM] 

Rep. Independent Electrical Contractors, Inc. 

Alternates 
Trevor N. Bowmer, Telcordia Technologies, NJ [U] 
(Alt. to James E. Brunssen) 
Rep. Alliance for Telecommunications Industry Solutions 



Terry C. Coleman, National Joint Apprentice & Training 
Committee, TN [L] 

(Alt. to Harold C. Ohde) 

Rep. International Brotherhood of Electrical Workers 
Timothy D. Cooke, Times Fiber Communications, Inc., 
VA [UT] 

(Alt. to Steven C. Johnson) 

Rep. National Cable & Telecommunications Association 
Jeff Fitzloff, State of Idaho Division of Building Safety, ID [E] 

(Alt. to Ron L. Janikowski) 

Rep. International Association of Electrical Inspectors 
John A. Kacperski, Tele Design Services, CA [M] 

(Alt. to Robert W. Jensen) 

Rep. Building Industry Consulting Services International 
Roderick S. Kalbfleisch, Northeast Utilities, CT [UT] 

(Alt. to Ralph M. Esemplare) 

Rep. Electric Light & Power Group/EEI 
Stanley Kaufman, CableSafe, Inc./OFS, GA [M] 

(Alt. to Gerald Lee Dorna) 

Rep. Insulated Cable Engineers Association Inc. 
David M. Lettkeman, Dish Network Service, LLC, CO [IM] 

(Alt. to George Bish) 

Rep. Satellite Broadcasting & Communications 

Association 
Jack McNamara, Bosch Security Systems, NY [M] 

(Alt. to J. Robert Boyer) 

Rep. National Electrical Manufacturers Association 
Craig Sato, Underwriters Laboratories Inc., CA [RT] 

(Alt. to Randolph J. Ivans) 
David B. Schrembeck, DBS Communications, Inc., OH [IM] 

(Alt. to Luigi G. Prezioso) 

Rep. Independent Electrical Contractors, Inc. 
Mario C. Spina, Verizon Wireless, OH [U] 

(Alt. to William J. McCoy) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
James T. Sudduth, Intertek Testing Services, KY [RT] 

(Alt. to Roland W. Gubisch) 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-19 



NATIONAL ELECTRICAL CODE COMMITTEE 



CODE-MAKING PANEL NO. 17 
Articles 422, 424, 426, 427, 680, 682 

Don W. Jhonson, Chair 
Interior Electric, Inc., FL [IM] 
Rep. National Electrical Contractors Association 



Thomas V. Blewitt, Underwriters Laboratories Inc., NY [RT] 
Paul Crivell, Camp, Dresser, & McKee Inc., WA [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Christopher S. Gill, New York Board of Fire Underwriters, 
NY [E] 

Bruce R. Hirsch, Baltimore Gas & Electric Company, 
MD [UT] 

Rep. Electric Light & Power Group/EEI 
James E. Maldonado, City of Tempe, AZ [E] 

Rep. International Association of Electrical Inspectors 
Wayne E. Morris, Association of Home Appliance 
Manufacturers, DC [M] 

(VL to 422, 424) 
Jurgen Pannock, Whirlpool Corporation, TN [M] 

Rep. Air-Conditioning, Heating, & Refrigeration Institute 

(VL to 422, 424) 
Marcos Ramirez, Hatfield-Reynolds Electric company, 
AZ [IM] 

Rep. Independent Electrical Contractors, Inc. 
Brian E. Rock, Hubbell Incorporated, CT [M] 

Rep. National Electrical Manufacturers Association 
Ronald F. Schapp, Intertek Testing Services, OH [RT] 
Kenneth M. Shell, Tyco Thermal Controls, CA [M] 

Rep. Copper Development Association Inc. 

(VL to 426, 427) 
Ronald Sweigart, E.I. duPont de Nemours & Company, Inc., 
DE [U] 

(VL to 422, 424, 426, 427, 682) 
Lee L. West, Newport Controls, LLC, CA [M] 

Rep. Association of Pool & Spa Professionals 

(VL to 680) 
Randy J. Yasenchak, IBEW Local Union 607, PA [L] 

Rep. International Brotherhood of Electrical Workers 

Alternates 
Dennis L. Baker, Springs & Sons Electrical Contractors 
Inc., AZ [IM] 

(Alt. to Marcos Ramirez) 

Rep. Independent Electrical Contractors, Inc. 



Bobby J. Gray, Hoydar/Buck, Inc., WA [IM] 

(Alt. to Don W. Jhonson) 

Rep. National Electrical Contractors Association 
E. P. Hamilton, III, E. P. Hamilton & Associates, Inc., TX [M] 

(Alt. to Lee L. West) 

Rep. Association of Pool & Spa Professionals 

(VL to 680) 
Robert M. Milatovich, Clark County Building Department, 
NV [E] 

(Alt. to James E. Maldonado) 

Rep. International Association of Electrical Inspectors 
Brian Myers, IBEW Local Union 98, PA [L] 

(Alt. to Randy J. Yasenchak) 

Rep. International Brotherhood of Electrical Workers 
Stephen C. Richbourg, Gulf Power Company, FL [UT] 

(Alt. to Bruce R. Hirsch) 

Rep. Electric Light & Power Group/EEI 
Patrick G. Salas, GE Consumer and Industrial, CT [M] 

(Alt. to Brian E. Rock) 

Rep. National Electrical Manufacturers Association 
Chester L. Sandberg, Shell Exploration & Production Inc., 
CA [U] 

(Alt. to Paul Crivell) 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Gary L. Siggins, Underwriters Laboratories Inc., CA [RT] 

(Alt. to Thomas V. Blewitt) 
Kam Fai Siu, Intertek, China [RT] 

(Alt. to Ronald F. Schapp) 

Nonvoting 

Douglas A. Lee, US Consumer Product Safety Commission, 
MD [C] 

(Alt. to Andrew M. Trotta) 
Andrew M. Trotta, US Consumer Product Safety 
Commission, MD [C] 

(Alt. to Douglas A. Lee) 



CODE-MAKING PANEL NO. 18 
Articles 406, 410, 411, 600, 605 

Michael N. Ber, Chair 
IEC, Houston, TX [IM] 
Rep. Independent Electrical Contractors, Inc. 



Frederick L. Carpenter, Lithonia Lighting, GA [M] 

Rep. National Electrical Manufacturers Association 
Paul Costello, NECA and IBEW Local 90 JATC, CT [L] 

Rep. International Brotherhood of Electrical Workers 
Lee C. Hewitt, Underwriters Laboratories Inc., IL [RT] 
Melvyn J. Kochan, Young Electric Sign Company, NV [M] 

Rep. International Sign Association 

(VL to 600) 
Steven A. Larson, MS Technology, Inc., TN [U] 

Rep. Institute of Electrical & Electronics Engineers, Inc. 
Amos D. Lowrance, Jr., City of Chattanooga, Tennessee, 
TN [E] 

Rep. International Association of Electrical Inspectors 
Michael S. O'Boyle, Philips-Lightolier, MA [M] 

Rep. American Lighting Association 

(VL to 410, 411) 
James F. Pierce, Intertek Testing Services, OR [RT] 



Sondra K. Todd, Westar Energy, Inc., KS [UT] 
Rep. Electric Light & Power Group/EEI 

Charles M. Trout, Maron Electric Company, FL [IM] 
Rep. National Electrical Contractors Association 

Jack Wells, Pass & Seymour/Legrand, NC [M] 

Randall K. Wright, RKW Consulting, PA [SE] 

Alternates 
Steve Campolo, Leviton Manufacturing Company, Inc., 

NY [M] 

(Alt. to Frederick L. Carpenter) 

Rep. National Electrical Manufacturers Association 
Robert T. Carlock, R. T Carlock Company, TN [IM] 

(Alt. to Michael N. Ber) 

Rep. Independent Electrical Contractors, Inc. 
Larry Chan, City of New Orleans, LA [E] 

(Alt. to Amos D. Lowrance, Jr.) 

Rep. International Association of Electrical Inspectors 



70-20 



NATIONAL ELECTRICAL CODE 201 1 Edition 



NATIONAL ELECTRICAL CODE COMMITTEE 



David D'Hooge, ComEd, IL [UT] 

(Alt. to Sondra K. Todd) 

Rep. Electric Light & Power Group/EEI 
Richard D. Gottwald, International Sign Association, VA [M] 

(Alt. to Melvyn J. Kochan) 

Rep. International Sign Association 

(VL to 600) 
Charles S. Korten, Underwriters Laboratories Inc., NY [RT] 

(Alt. to Lee C. Hewitt) 



Terry K. McGowan, Lighting Ideas, Inc., OH [M] 

(Alt. to Michael S. O'Boyle) 

Rep. American Lighting Association 

(VL to 410, 411) 
Jesse Sprinkle, IBEW Local 461, IL [L] 

(Alt. to Paul Costello) 

Rep. International Brotherhood of Electrical Workers 
Chandresh Thakur, Intertek Testing Services, CA [RT] 

(Alt. to James F. Pierce) 



CODE-MAKING PANEL NO. 19 
Articles 545, 547, 550, 551, 552, 553, 555, 604, 675, and Annex D, Examples Dll and D12 



Leslie Sabin-Mercado, Chair 
San Diego Gas & Electric Company, CA [UT] 
Rep. Electric Light & Power Group/EEI 



Barry S. Bauman, Alliant Energy, WI [U] 

Rep. American Society of Agricultural & Biological 

Engineers 
Ron B. Chilton, North Carolina Department of Insurance, 
NC [E] 

Rep. International Association of Electrical Inspectors 
Garry D. Cole, Shelby/Mansfield KOA, OH [U] 

Rep. National Association of RV Parks & Campgrounds 

(VL to 550, 551, 552) 
Steven R. Goodman, Alcan Cable, PA [M] 

Rep. The Aluminum Association, Inc. 
Bruce A. Hopkins, Recreation Vehicle Industry Association, 
VA [M] 

(VL to 550, 551, 552) 
Howard D. Hughes, Hughes Electric Company Inc., AR [IM] 

Rep. National Electrical Contractors Association 
David W. Johnson, CenTex IEC, TX [IM] 

Rep. Independent Electrical Contractors, Inc. 
Thomas R. Lichtenstein, Underwriters Laboratories Inc., 
IL [RT] 
Timothy P. McNeive, Thomas & Betts Corporation, TN [M] 

Rep. National Electrical Manufacturers Association 
Ronald Michaelis, South Bend & Vicinity Electrical JATC, 
IN [L] 

Rep. International Brotherhood of Electrical Workers 
Doug Mulvaney, Kampgrounds of America, Inc., MT [U] 

(VLto550, 551, 552,555) 
Michael L. Zieman, RADCO, CA [RT] 

(VLto545, 550, 551,552) 

Alternates 

Glenn H. Ankenbrand, Delmarva Power, MD [UT] 
(Alt. to Leslie Sabin-Mercado) 
Rep. Electric Light & Power Group/EEI 



Michael B. F. Atkinson, Kampgrounds of America, Inc., 
MT[U] 

(Alt. to Doug Mulvaney) 

(VLto 550, 551, 552, 555) 
William Bruce Bowman, Fox Systems, Inc., GA [IM] 

(Alt. to David W. Johnson) 

Rep. Independent Electrical Contractors, Inc. 
Robert J. Fick, Alliant Energy, WI [U] 

(Alt. to Barry S. Bauman) 

Rep. American Society of Agricultural & Biological 

Engineers 
John P. Goodsell, Hubbell Incorporated, CT [M] 

(Alt. to Timothy P. McNeive) 

Rep. National Electrical Manufacturers Association 
Kent Perkins, Recreation Vehicle Industry Association, VA [M] 

(Alt. to Bruce A. Hopkins) 

(VLto 550, 551, 552) 
Raymond F. Thicker, Consulting Professional 
Engineer/RADCO, CA [RT] 

(Alt. to Michael L. Zieman) 

(VLto 545, 550, 551, 552) 
Ronald D. Weaver, Jr., North Alabama Electrical JATC, 
AL [L] 

(Alt. to Ronald Michaelis) 

Rep. International Brotherhood of Electrical Workers 
Cari Williamette, City of St. Paul, MN [E] 

(Alt. to Ron B. Chilton) 

Rep. International Association of Electrical Inspectors 
Eugene W. Wirth, Underwriters Laboratories Inc., WA [RT] 

(Alt. to Thomas R. Lichtenstein) 



NFPA Electrical Engineering Division Technical Staff 

William Burke, Division Manager 

Mark W. Earley, Chief Electrical Engineer 

Mark Cloutier, Senior Electrical Engineer 

Christopher Coache, Senior Electrical Engineer 

Jean A. O'Connor, Electrical Project Specialist/Support 

Supervisor 

Lee F. Richardson, Senior Electrical Engineer 

Richard J. Roux, Senior Electrical Specialist 

Jeffrey S. Sargent, Senior Electrical Specialist 



Support Staff 

Carol Henderson 
Mary Warren-Pilson 
Kimberly Shea 

NFPA Staff Editors 

Pamela Nolan 
Kim Cervantes 



Note: Membership on a committee shall not in and of itself constitute an endorsement of the Association or any document developed by 
the Committee on which the member serves. 

Committee Scope: This Committee shall have primary responsibility for documents on minimizing the risk of electricity as a source of 
electric shock and as a potential ignition source of fires and explosions. It shall also be responsible for text to minimize the propagation 
of fire and explosions due to electrical installations. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-21 



90.1 



ARTICLE 90 — INTRODUCTION 



NFPA 70 
National Electrical Code® 

2011 Edition 

IMPORTANT NOTE: This NFPA document is made 
available for use subject to important notices and legal 
disclaimers. These notices and disclaimers appear in all 
publications containing this document and may be found 
under the heading "Important Notices and Disclaimers 
Concerning NFPA Documents." They can also be ob- 
tained on request from NFPA or viewed at 
www.nfpa.org/disclaimers. 

This 201 1 edition includes the following usability fea- 
tures as aids to the user. Changes other than editorial are 
highlighted with gray shading within sections and with ver- 
tical ruling for large blocks of changed or new text and for 
new tables and changed or new figures. Where one or more 
complete paragraphs have been deleted, the deletion is in- 
dicated by a bullet (•) between the paragraphs that remain. 
The index now has dictionary-style headers with helpful 
identifiers at the top of every index page. 



ARTICLE 90 
Introduction 



90.1 Purpose. 

(A) Practical Safeguarding. The purpose of this Code is 
the practical safeguarding of persons and property from 
hazards arising from the use of electricity. 

(B) Adequacy. This Code contains provisions that are con- 
sidered necessary for safety. Compliance therewith and 
proper maintenance results in an installation that is essen- 
tially free from hazard but not necessarily efficient, conve- 
nient, or adequate for good service or future expansion of 
electrical use. 

Informational Note: Hazards often occur because of over- 
loading of wiring systems by methods or usage not in con- 
formity with this Code. This occurs because initial wiring 
did not provide for increases in the use of electricity. An 
initial adequate installation and reasonable provisions for 
system changes provide for future increases in the use of 
electricity. 

(C) Intention. This Code is not intended as a design speci- 
fication or an instruction manual for untrained persons. 

(D) Relation to Other International Standards. The re- 
quirements in this Code address the fundamental principles 
of protection for safety contained in Section 131 of Inter- 



national Electrotechnical Commission Standard 60364-1, 
Electrical Installations of Buildings. 

Informational Note: IEC 60364-1, Section 131, contains 
fundamental principles of protection for safety that encom- 
pass protection against electric shock, protection against 
thermal effects, protection against overcurrent, protection 
against fault currents, and protection against overvoltage. 
All of these potential hazards are addressed by the require- 
ments in this Code. 

90.2 Scope. 

(A) Covered. This Code covers the installation of electrical 
conductors, equipment, and raceways; signaling and commu- 
nications conductors, equipment, and raceways; and optical 
fiber cables and raceways for the following: 

(1) Public and private premises, including buildings, struc- 
tures, mobile homes, recreational vehicles, and floating 
buildings 

(2) Yards, lots, parking lots, carnivals, and industrial sub- 
stations 

(3) Installations of conductors and equipment that connect 
to the supply of electricity 

(4) Installations used by the electric utility, such as office 
buildings, warehouses, garages, machine shops, and 
recreational buildings, that are not an integral part of a 
generating plant, substation, or control center. 

(B) Not Covered. This Code does not cover the following: 

(1) Installations in ships, watercraft other than floating build- 
ings, railway rolling stock, aircraft, or automotive vehicles 
other than mobile homes and recreational vehicles 

Informational Note: Although the scope of this Code in- 
dicates that the Code does not cover installations in ships, 
portions of this Code are incorporated by reference into 
Title 46, Code of Federal Regulations, Parts 110-1 13. 

(2) Installations underground in mines and self-propelled 
mobile surface mining machinery and its attendant 
electrical trailing cable 

(3) Installations of railways for generation, transformation, 
transmission, or distribution of power used exclusively 
for operation of rolling stock or installations used ex- 
clusively for signaling and communications purposes 

(4) Installations of communications equipment under the 
exclusive control of communications utilities located 
outdoors or in building spaces used exclusively for 
such installations 

(5) Installations under the exclusive control of an electric 
utility where such installations 

a. Consist of service drops or service laterals, and as- 
sociated metering, or 

b. Are on property owned or leased by the electric 
utility for the purpose of communications, metering, 



70-22 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 90 — INTRODUCTION 



90.5 



generation, control, transformation, transmission, or 
distribution of electric energy, or 

c Are lowVivi wi legally establishes easements 01 
rights of way, or 

d. Are located by otiiti written agreements s ither des- 
ignated b- 01 recognized b} (inliiic service commis- 
sions, ut''itv commis ion 01 otht i reg ilatory agen- 
cies having ji.irist.1k tion for such installations. These 
written agreement shall be limited to installations 
for the purpose of communications metering, gen- 
eration, control, transformation transmission, or 
distribution of electric energy where Lg;;l!y estab- 
lished eas ments 01 rights-of-waj cannot be ob- 
tained. 1iie>,e installati ins ••Itjll i«- limited >o I -V-al 
lands, native American reservations through the 
U.S. Department ot fhv. Interioi Bureau of Indian 
Affairs. iniiitM", bases, lands controlled by port an- 
tiiorilk . nil state tgencie and departments;, .mi 
land 1 , owned by railroads 

Informational Note to (4) and (5): Examples of utilities may 
include those entities that are typically designated or recognized 
by governmental law or regulation by public service/utility com- 
missions and that install, operate, and maintain electric supply 
(such as generation, transmission, or distribution systems) or 
communications systems (such as telephone, CATV, Internet, sat- 
ellite, or data services). Utilities may be subject to compliance 
with codes and standards covering their regulated activities as 
adopted under governmental law or regulation. Additional infor- 
mation can be found through consultation with the appropriate 
governmental bodies, such as state regulatory commissions, the 
Federal Energy Regulatory Commission, and the Federal Com- 
munications Commission. 

(C) Special Permission. The authority having jurisdiction 
for enforcing this Code may grant exception for the instal- 
lation of conductors and equipment that are not under the 
exclusive control of the electric utilities and are used to 
connect the electric utility supply system to the sen e 
conductors of the premises served, provided such installa- 
tions are outside a building or structure, or terminate inside 
nearest the pomr >>r entrance at '.he service • undue-tors. 

90.3 Code Arrangement. This Code is divided into the 
introduction and nine chapters, as shown in Figure 90.3. 
Chapters 1, 2, 3, and 4 apply generally; Chapters 5, 6, and 
7 apply to special occupancies, special equipment, or other 
special conditions. These latter chapters supplement or modify 
the general rules. Chapters 1 through 4 apply except as 
amended by Chapters 5, 6, and 7 for the particular conditions. 

Chapter 8 covers communications systems and is not sub- 
ject to the requirements of Chapters 1 through 7 except where 
the requirements are specifically referenced in Chapter 8. 

Chapter 9 consists of tables that are applicable as refer- 
enced. 

Informative annexes are not part of the requirements of 
this Code but are included for informational purposes only. 



Chapter 1 — General 



Chapter 2 — Wiring and Protection 



Chapter 3 — Wiring Methods and Materials 



Chapter 4 — Equipment for General Use 



Applies generally 
*■ to all electrical 
installations 



Supplements or modifies 
Chapters 1 through 4 



Chapter 5 — Special Occupancies 



Chapter 6 — Special Equipment 



Chapter 7 — Special Conditions 



Chapter 8 is not subject 
to the requirements of 

Chapter 8 - Communications Systems] } ^^^ff^^^ 

specifically referenced in 
Chapter 8. 

I f- Applicable as referenced 
Informational only; 



Chapter 9 — Tables 



Informative Annex A through 
Informative Annex I 



not mandatory 



Figure 90.3 Code Arrangement. 



90.4 Enforcement. This Code is intended to be suitable 
for mandatory application by governmental bodies that ex- 
ercise legal jurisdiction over electrical installations, includ- 
ing signaling and communications systems, and for use by 
insurance inspectors. The authority having jurisdiction for 
enforcement of the Code has the responsibility for making 
interpretations of the rules, for deciding on the approval of 
equipment and materials, and for granting the special per- 
mission contemplated in a number of the rules. 

By special permission, the authority having jurisdiction 
may waive specific requirements in this Code or permit 
alternative methods where it is assured that equivalent ob- 
jectives can be achieved by establishing and maintaining 
effective safety. 

This Code may require new products, constructions, or 
materials that may not yet be available at the time the Code 
is adopted. In such event, the authority having jurisdiction 
may permit the use of the products, constructions, or mate- 
rials that comply with the most recent previous edition of 
this Code adopted by the jurisdiction. 

90.5 Mandatory Rules, Permissive Rules, and Explana- 
tory Material. 

(A) Mandatory Rules. Mandatory rules of this Code are 
those that identify actions that are specifically required or 
prohibited and are characterized by the use of the terms 
shall or shall not. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-23 



90.6 



ARTICLE 90 — INTRODUCTION 



(B) Permissive Rules. Permissive rules of this Code are 
those that identify actions that are allowed but not required, 
are normally used to describe options or alternative meth- 
ods, and are characterized by the use of the terms shall be 
permitted or shall not be required. 

(C) Explanatory Material. Explanatory material, such as 
references to other standards, references to related sections 
of this Code, or information related to a Code rule, is in- 
cluded in this Code in the form of informational notes. 
Such notes are informational only and are not enforceable 
as requirements of this Code. 

Brackets containing section references to another NFPA 
document are for informational purposes only and are pro- 
vided as a guide to indicate the source of the extracted text. 
These bracketed references immediately follow the ex- 
tracted text. 

Informational Note: The format and language used in this 
Code follows guidelines established by NFPA and pub- 
lished in the NEC Style Manual. Copies of this manual can 
be obtained from NFPA. 

(D) Informative Annexes. Nonrmnclytoyy information 
relative to the use of the NEC is provided in informative 
annexe Informative innexes m n.ol part of the enforce 
able requirements of the NEC. but are included for infor- 
tii'i'i ;F' pmpov.'- .inly. 

90.6 Formal Interpretations. To promote uniformity of 
interpretation and application of the provisions of this 
Code, formal interpretation procedures have been estab- 
lished and are found in the NFPA Regulations Governing 
Committee Projects. 

90.7 Examination of Equipment for Safety. For specific 
items of equipment and materials referred to in this Code, 
examinations for safety made under standard conditions 
provide a basis for approval where the record is made gen- 
erally available through promulgation by organizations 
properly equipped and qualified for experimental testing, 
inspections of the run of goods at factories, and service- 
value determination through field inspections. This avoids 
the necessity for repetition of examinations by different 
examiners, frequently with inadequate facilities for such 
work, and the confusion that would result from conflicting 
reports on the suitability of devices and materials examined 
for a given purpose. 

It is the intent of this Code that factory-installed inter- 
nal wiring or the construction of equipment need not be 
inspected at the time of installation of the equipment, ex- 
cept to detect alterations or damage, if the equipment has 
been listed by a qualified electrical testing laboratory that is 
recognized as having the facilities described in the preced- 



ing paragraph and that requires suitability for installation in 
accordance with this Code. 

Informational Note No. I: See requirements in 110.3. 

Informational Note No. 2: Listed is defined in Article 100. 

Informational Note No. 3: Informative Annex A contains 
an informative list of product safety standards for electrical 
equipment. 

90.8 Wiring Planning. 

(A) Future Expansion and Convenience. Plans and specifi- 
cations that provide ample space in raceways, spare raceways, 
and additional spaces allow for future increases in electric 
power and communications circuits. Distribution centers lo- 
cated in readily accessible locations provide convenience and 
safety of operation. 

(B) Number of Circuits in Enclosures. It is elsewhere pro- 
vided in this Code that the number of wires and circuits con- 
fined in a single enclosure be varyingly restricted. Limiting the 
number of circuits in a single enclosure minimizes the effects 
from a short circuit or ground fault in one circuit. 

90.9 Units of Measurement. 

(A) Measurement System of Preference. For the purpose 
of this Code, metric units of measurement are in accor- 
dance with the modernized metric system known as the 
International System of Units (SI). 

(B) Dual System of Units. SI units shall appear first, and 
inch-pound units shall immediately follow in parentheses. 
Conversion from inch-pound units to SI units shall be 
based on hard conversion except as provided in 90.9(C). 

(C) Permitted Uses of Soft Conversion. The cases given 
in 90.9(C)(1) through (C)(4) shall not be required to use hard 
conversion and shall be permitted to use soft conversion. 

(1) Trade Sizes. Where the actual measured size of a prod- 
uct is not the same as the nominal size, trade size designa- 
tors shall be used rather than dimensions. Trade practices 
shall be followed in all cases. 

(2) Extracted Material. Where material is extracted from 
another standard, the context of the original material shall 
not be compromised or violated. Any editing of the ex- 
tracted text shall be confined to making the style consistent 
with that of the NEC. 

(3) Industry Practice. Where industry practice is to ex- 
press units in inch-pound units, the inclusion of SI units 
shall not be required. 

(4) Safety. Where a negative impact on safety would re- 
sult, soft conversion shall be used. 



70-24 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 90 — INTRODUCTION 90.9 



(D) Compliance. Conversion from inch-pound units to SI sizes that might or might not be interchangeable with the 

units Shall be permitted to be an approximate conversion. sizes used in the original measurement. Soft conversion is 

v „ considered a direct mathematical conversion and involves a 

Compliance with the numbers shown in either the SI sys- change in the description of an existing measurement but 

tern or the inch-pound system shall constitute compliance no t in the actual dimension. 

with this Code. Informational Note No. 2: SI conversions are based on 

1EEE/ASTM SI 10-1997, Standard for the Use of the Inter- 

Informational Note No. 1: Hard conversion is considered national System of Units (SI): The Modern Metric System. 
a change in dimensions or properties of an item into new 



2011 Edition NATIONAL ELECTRICAL CODE 70 25 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



Chapter 1 General 



ARTICLE 100 

[. Definitions.. 

Scope. This article contains only those definitions essential 
to the proper application of this Code. It is not intended to 
include commonly defined general terms or commonly de- 
fined technical terms from related codes and standards. In 
general, only those terms that are used in two or more 
articles are defined in Article 100. Other definitions are 
included in the article in which they are used but may be 
referenced in Article 100. 

Part I of this article contains definitions intended to 
apply wherever the terms are used throughout this Code. 
Part II contains definitions applicable only to the parts of 
articles specifically covering installations and equipment 
operating at over 600 volts, nominal. 

I. Genera] 

Accessible (as applied to equipment). Admitting close 
approach; not guarded by locked doors, elevation, or other 
effective means. 

Accessible (as applied to wiring methods). Capable of 
being removed or exposed without damaging the building 
structure or finish or not permanently closed in by the struc- 
ture or finish of the building. 

Accessible, Readily (Readily Accessible). Capable of be- 
ing reached quickly for operation, renewal, or inspections 
without requiring those to whom ready access is requisite 
to climb over or remove obstacles or to resort to portable 
ladders, and so forth. 

Ampacity. The maximum current, in amperes, that a con- 
ductor can carry continuously under the conditions of use 
without exceeding its temperature rating. 

Appliance. Utilization equipment, generally other than in- 
dustrial, that is normally built in standardized sizes or types 
and is installed or connected as a unit to perform one or 
more functions such as clothes washing, air conditioning, 
food mixing, deep frying, and so forth. 

Approved. Acceptable to the authority having jurisdiction. 

Arc-Fault Circuit Interrupter (AFCI). A device intended 
to provide protection from ilio effects of arc ft'*, h\ rec- 
ognizing character] tics imiqu. to arcing and by function- 



ing lo de-enertii/e the 



tiiiLiii v»ii> H jii in i ill < ts 'JCCV 



ted. 



Askarel. A generic term for a group of nonflammable syn- 
thetic chlorinated hydrocarbons used as electrical insulating 



media. Askarels of various compositional types are used. 
Under arcing conditions, the gases produced, while consist- 
ing predominantly of noncombustible hydrogen chloride, 
can include varying amounts of combustible gases, depend- 
ing on the askarel type. 

Attachment Plug (Plug Cap) (Plug). A device that, by 
insertion in a receptacle, establishes a connection between 
the conductors of the attached flexible cord and the conduc- 
tors connected permanently to the receptacle. 

Authority Having Jurisdiction (AHJ). An organization, 
office, or individual responsible for enforcing the require- 
ments of a code or standard, or for approving equipment, 
materials, an installation, or a procedure. 

Informational Note: The phrase "authority having jurisdic- 
tion," or its acronym AHJ, is used in NFPA documents in a 
broad manner, since jurisdictions and approval agencies 
vary, as do their responsibilities. Where public safety is 
primary, the authority having jurisdiction may be a federal, 
state, local, or other regional department or individual such 
as a fire chief; fire marshal; chief of a fire prevention bu- 
reau, labor department, or health department; building offi- 
cial; electrical inspector; or others having statutory author- 
ity. For insurance purposes, an insurance inspection 
department, rating bureau, or other insurance company rep- 
resentative may be the authority having jurisdiction. In 
many circumstances, the property owner or his or her des- 
ignated agent assumes the role of the authority having ju- 
risdiction; at government installations, the commanding of- 
ficer or departmental official may be the authority having 
jurisdiction. 

Automatic. Performing a function w ithout the necessity of 
human intervention. 

Bathroom. An area including a basin with one or more of 
the following: a toilet, a urinal, a tub, a shower, a bidet, or 
similar plumbing fixtures. 

Bonded (Bonding). Connected to establish electrical con- 
tinuity and conductivity. 

Bonding Conductor or Jumper. A reliable conductor to 
ensure the required electrical conductivity between metal 
parts required to be electrically connected. 

Bonding Jumper, Equipment. The connection between two 
or more portions of the equipment grounding conductor. 

Bonding Jumper, Main. The connection between the 
grounded circuit conductor and the equipment grounding 
conductor at the service. 

Bonding Jumper, System. The connection between the 
grounded circuit conductoi and the supply-side bonding 



70-26 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 100 — DEFINITIONS 



CHAPTER 1 



jumper, or the equipment grounding conductor cr both, at a 
separately derived system. 

Branch Circuit. The circuit conductors between the final 
overcurrent device protecting the circuit and the outlet(s). 

Branch Circuit, Appliance. A branch circuit that supplies 
energy to one or more outlets to which appliances are to be 
connected and that has no permanently connected lumi- 
naires that are not a part of an appliance. 

Branch Circuit, General-Purpose. A branch circuit that 
supplies two or more receptacles or outlets for lighting and 
appliances. 

Branch Circuit, Individual. A branch circuit that supplies 
only one utilization equipment. 

Branch Circuit, Multiwire. A branch circuit that consists 
of two or more ungrounded conductors that have a voltage 
between them, and a grounded conductor that has equal 
voltage between it and each ungrounded conductor of the 
circuit and that is connected to the neutral or grounded 
conductor of the system. 

Building. A structure that stands alone or that is cut off 
from adjoining structures by fire walls with all openings 
therein protected by approved fire doors. 

Cabinet. An enclosure that is designed for either surface 
mounting or flush mounting and is provided with a frame, 
mat, or trim in which a swinging door or doors are or can 
be hung. 

Circuit Breaker. A device designed to open and close a 
circuit by nonautomatic means and to open the circuit au- 
tomatically on a predetermined overcurrent without damage 
to itself when properly applied within its rating. 

Informational Note: The automatic opening means can be 
integral, direct acting with the circuit breaker, or remote 
from the circuit breaker. 

Adjustable (as applied to circuit breakers). A qualifying 
term indicating that the circuit breaker can be set to trip at 
various values of current, time, or both, within a predeter- 
mined range. 

Instantaneous Trip (as applied to circuit breakers). A 
qualifying term indicating that no delay is purposely intro- 
duced in the tripping action of the circuit breaker. 

Inverse Time (as applied to circuit breakers). A qualifying 
term indicating that there is purposely introduced a delay in 
the tripping action of the circuit breaker, which delay de- 
creases as the magnitude of the current increases. 

Nonadjustable (as applied to circuit breakers). A quali- 
fying term indicating that the circuit breaker does not have 
any adjustment to alter the value of current at which it will 
trip or the time required for its operation. 



Setting (of circuit breakers). The value of current, time, or 
both, at which an adjustable circuit breaker is set to trip. 

Clothes Closet. A non-habitable room or space intended 
primarily for storage of garments and apparel. 

Communications Equipment. The electronic equipment 
that performs the telecommunications operations for the 
transmission of audio, video, and data, and includes power 
equipment (e.g., dc converters, inverters, and batteries) and 
technical support equipment (e.g., computers). 

Concealed. Rendered inaccessible by the structure or finish 
of the building. Wires in concealed raceways are consid- 
ered concealed, even though they may become accessible 
by withdrawing them. 

Conductor, Bare. A conductor having no covering or elec- 
trical insulation whatsoever. 

Conductor, Covered. A conductor encased within material 
of composition or thickness that is not recognized by this 
Code as electrical insulation. 

Conductor, Insulated. A conductor encased within mate- 
rial of composition and thickness that is recognized by this 
Code as electrical insulation. 

Conduit Body. A separate portion of a conduit or tubing 
system that provides access through a removable cover(s) 
to the interior of the system at a junction of two or more 
sections of the system or at a terminal point of the system. 
Boxes such as FS and FD or larger cast or sheet metal 
boxes are not classified as conduit bodies. 

Connector, Pressure (Solderless). A device that establishes 
a connection between two or more conductors or between 
one or more conductors and a terminal by means of me- 
chanical pressure and without the use of solder. 

Continuous Load. A load where the maximum current is 
expected to continue for 3 hours or more. 

Controller. A device or group of devices that serves to 
govern, in some predetermined manner, the electric power 
delivered to the apparatus to which it is connected. 

Cooking Unit, Counter-Mounted. A cooking appliance 
designed for mounting in or on a counter and consisting of 
one or more heating elements, internal wiring, and built-in 
or mountable controls. 

Coordination (Selective). Localization of an overcurrent 
condition to restrict outages to the circuit or equipment 
affected, accomplished by the choice of overcurrent protec- 
tive devices and their ratings or settings. 

Copper-Clad Aluminum Conductors. Conductors drawn 
from a copper-clad aluminum rod with the copper metallur- 
gically bonded to an aluminum core. The copper forms a 



20 1 1 Edition NATIONAL ELECTRICAL CODE 



70-27 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



minimum of 10 percent of the cross-sectional area of a 
solid conductor or each strand of a stranded conductor. 

Cutout Box. An enclosure designed for surface mounting 
that has swinging doors or covers secured directly to and 
telescoping with the walls of the box proper. 

Dead Front. Without live parts exposed to a person on the 
operating side of the equipment. 

Demand Factor. The ratio of the maximum demand of a 
system, or part of a system, to the total connected load of a 
system or the part of the system under consideration. 

Device. A unit of an electrical system that carries or con- 
trols electric energy as its principal function. 

Disconnecting Means. A device, or group of devices, or 
other means by which the conductors of a circuit can be 
disconnected from their source of supply. 

Dusttight. Constructed so that dust will not enter the en- 
closing case under specified test conditions. 

Duty, Continuous. Operation at a substantially constant 
load for an indefinitely long time. 

Duty, Intermittent. Operation for alternate intervals of (1) 
load and no load; or (2) load and rest; or (3) load, no load, 
and rest. 

Duty, Periodic. Intermittent operation in which the load 
conditions are regularly recurrent. 

Duty, Short-Time. Operation at a substantially constant 
load for a short and definite, specified time. 

Duty, Varying. Operation at loads, and for intervals of 
time, both of which may be subject to wide variation. 

Dwelling, One-Family. A building that consists solely of 
one dwelling unit. 

Dwelling, Two-Family. A building that consists solely of 
two dwelling units. 

Dwelling, Multifamily. A building that contains three or 
more dwelling units. 

Dwelling Unit. A single unit, providing complete and in- 
dependent living facilities for one or more persons, includ- 
ing permanent provisions for living, sleeping, cooking, and 
sanitation. 

Electric Sign. A fixed, stationary, or portable self-contained, 
electrically illuminated utilization equipment with words or 
symbols designed to convey information or attract attention. 

Electric Power Production and Distribution Network. 

Power production, distribution, and utilization equipment 
and facilities, such as electric utility systems that deliver 



electric power to the connected loads, that are external to 
and not controlled by an interactive system. 

Enclosed. Surrounded by a case, housing, fence, or wall(s) 
that prevents persons from accidentally contacting ener- 
gized parts. 

Enclosure. The case or housing of apparatus, or the fence 
or walls surrounding an installation to prevent personnel 
from accidentally contacting energized parts or to protect 
the equipment from physical damage. 

Informational Note: See Table 1 10.28 for examples of en- 
closure types. 

Energized. Electrically connected to, or is, a source of 
voltage. 

Equipment. A general term, including fittings, devices, appli- 
ances, luminaires, apparatus, machinery, and the like used as a 
part of, or in connection with, an electrical installation. 

Explosionproof Equipment, t.'.jmjjjnent enclosed in a case 
that is capable of withstanding an explosion of a specified gas 
or vapor that may occur within it and of preventing the igni- 
tion of a specified gas or vapor surrounding the enclosure by 
sparks, flashes, or explosion of the gas or vapor within, and 
that operates at such an external temperature that a surround- 
ing flammable atmosphere will not be ignited thereby. 

Informational Note: For further information, see ANSI/UL 
1203-2006. Explosion-Proof and Dust-Ignition- Proof Electri- 
cal Equipment for Use in Hazardous (Classified) Locations. 

Exposed (as applied to live parts). Capable of being in- 
advertently touched or approached nearer than a safe dis- 
tance by a person. It is applied to parts that are not suitably 
guarded, isolated, or insulated. 

Exposed (as applied to wiring methods). On or attached 
to the surface or behind panels designed to allow access. 

Externally Operable. Capable of being operated without 
exposing the operator to contact with live parts. 

Feeder. All circuit conductors between the service equip- 
ment, the source of a separately derived system, or other 
power supply source and the final branch-circuit overcur- 
rent device. 

Festoon Lighting. A string of outdoor lights that is sus- 
pended between two points. 

Fitting. An accessory such as a locknut, bushing, or other 
part of a wiring system that is intended primarily to per- 
form a mechanical rather than an electrical function. 

Garage. A building or portion of a building in which one or 
more self-propelled vehicles can be kept for use, sale, stor- 
age, rental, repair, exhibition, or demonstration purposes. 

Informational Note: For commercial garages, repair and 
storage, see Article 511. 



70-28 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 100 — DEFINITIONS 



CHAPTER 1 



Ground. The earth. 

Ground I'mitt. An unintentional, electrical!) conducting 
connection between an ungrounded con'ductoi of an electri- 
cal circuit ;vm the normally non-current-carrying conduc- 
tors, menfh- enclosures. m<-''.ltu. raceways, ukijIIjc equip- 
ment, or cai 111. 

Grounded (Grounding). Connected (connecting) to 
ground or to a conductive body that extends the ground 
connection. 

Grounded, Solidly. Connected to ground without inserting 
any resistor or impedance device. 

Grounded Conductor. A system or circuit conductor that 
is intentionally grounded. 

Ground-Fault Circuit Interrupter (GFCI). A device in- 
tended for the protection of personnel that functions to de- 
energize a circuit or portion thereof within an established 
period of time when a current to ground exceeds the values 
established for a Class A device. 

Informational Note: Class A ground-fault circuit interrupt- 
ers trip when the current to ground is 6 mA or higher and 
do not trip when the current to ground is less than 4 mA. 
For further information, see UL 943, Standard for Ground- 
Fault Circuit Interrupters. 

Ground-Fault Protection of Equipment. A system in- 
tended to provide protection of equipment from damaging 
line-to-ground fault currents by operating to cause a discon- 
necting means to open all ungrounded conductors of the 
faulted circuit. This protection is provided at current levels less 
than those required to protect conductors from damage 
through the operation of a supply circuit overcurrent device. 

Grounding Conductor, Equipment (EGC). The conduc- 
tive path(s) installed to connect normally non-current-carrying 
metal parts of equipment together and to the system grounded 
conductor or to the grounding electrode conductor, or both. 

Informational Note No. 1: It is recognized that the equip- 
ment grounding conductor also performs bonding. 

Informational Note No. 2: See 250. 1 1 8 for a list of accept- 
able equipment grounding conductors. 

Grounding Electrode. A conducting object through which 
a direct connection to earth is established. 

Grounding Electrode Conductor. A conductor used to 
connect the system grounded conductor or the equipment to 
a grounding electrode or to a point on the grounding elec- 
trode system. 

Guarded. Covered, shielded, fenced, enclosed, or other- 
wise protected by means of suitable covers, casings, barri- 
ers, rails, screens, mats, or platforms to remove the likeli- 



hood of approach or contact by persons or objects to a point 
of danger. 

Guest Room. An accommodation combining living, sleep- 
ing, sanitary, and storage facilities within a compartment. 

Guest Suite. An accommodation with two or more con- 
tiguous rooms comprising a compartment, with or without 
doors between such rooms, that provides living, sleeping, 
sanitary, and storage facilities. 

Handhole Enclosure. An enclosure for use in underground 
systems, provided with an open or closed bottom, and sized 
to allow personnel to reach into, but not enter, for the pur- 
pose of installing, operating, or maintaining equipment or 
wiring or both. 

Hoistway. Any shaftway, hatchway, well hole, or other ver- 
tical opening or space in which an elevator or dumbwaiter 
is designed to operate. 

Identified (as applied to equipment). Recognizable as 
suitable for the specific purpose, function, use, environ- 
ment, application, and so forth, where described in a par- 
ticular Code requirement. 

Informational Note: Some examples of ways to determine 
suitability of equipment for a specific purpose, environment, 
or application include investigations by a qualified testing 
laboratory (listing and labeling), an inspection agency, or other 
organizations concerned with product evaluation. 

In Sight From (Within Sight From, Within Sight). 

Where this Code specifies that one equipment shall be "in 
sight from," "within sight from," or "within sight of," and 
so forth, another equipment, the specified equipment is to be 
visible and not more than 15 m (50 ft) distant from the other. 

Interactive System. An electric power production system 
that is operating in parallel with and capable of delivering 
energy to an electric primary source supply system. 

Interrupting Rating. The highest current at rated voltage 
that a device is identified to interrupt under standard test 
conditions. 

Informational Note: Equipment intended to interrupt cur- 
rent at other than fault levels may have its interrupting 
rating implied in other ratings, such as horsepower or 
locked rotor current. 

Intersystem Bonding Termination. A device that pro- 
vides a means for connecting bonding vOfid'jctoi'-. for com- 
munications systems tc the > oundin ; el etrode •-' >ts m 

Isolated (as applied to location). Not readily accessible 
to persons unless special means for access are used. 

Kitchen. An area with a sink and permanent provi- ions for 
food preparation and cooking. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-29 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



Labeled. Equipment or materials to which has been at- 
tached a label, symbol, or other identifying mark of an 
organization that is acceptable to the authority having juris- 
diction and concerned with product evaluation, that main- 
tains periodic inspection of production of labeled equip- 
ment or materials, and by whose labeling the manufacturer 
indicates compliance with appropriate standards or perfor- 
mance in a specified manner. 

Lighting Outlet. An outlet intended for the direct connec- 
tion of a lampholder or luminaire. 

Listed. Equipment, materials, or services included in a list 
published by an organization that is acceptable to the au- 
thority having jurisdiction and concerned with evaluation 
of products or services, that maintains periodic inspection 
of production of listed equipment or materials or periodic 
evaluation of services, and whose listing states that either 
the equipment, material, or service meets appropriate des- 
ignated standards or has been tested and found suitable for 
a specified purpose. 

Informational Note: The means for identifying listed 
equipment may vary for each organization concerned with 
product evaluation, some of which do not recognize equip- 
ment as listed unless it is also labeled. Use of the system 
employed by the listing organization allows the authority 
having jurisdiction to identify a listed product. 

Live Parts. Energized conductive components. 

Location, Damp. Locations protected from weather and 
not subject to saturation with water or other liquids but 
subject to moderate degrees of moisture. Examples of such 
locations include partially protected locations under cano- 
pies, marquees, roofed open porches, and like locations, 
and interior locations subject to moderate degrees of mois- 
ture, such as some basements, some barns, and some cold- 
storage warehouses. 

Location, Dry. A location not normally subject to damp- 
ness or wetness. A location classified as dry may be tem- 
porarily subject to dampness or wetness, as in the case of a 
building under construction. 

Location, Wet. Installations underground or in concrete 
slabs or masonry in direct contact with the earth; in loca- 
tions subject to saturation with water or other liquids, such 
as vehicle washing areas; and in unprotected locations ex- 
posed to weather. 

Luminaire. A complete lighting unit consisting of a light 
source such as a lamp or lamps, together with the parts 
designed to position the light source and connect it to the 
power supply. It may also include parts to protect the light 
source or the ballast or to distribute the light. A lampholder 
itself is not a luminaire. 



Metal-Enclosed Power Switchgear. A switchgear assem- 
bly completely enclosed on all sides and top with sheet 
metal (except for ventilating openings and inspection win- 
dows) and containing primary power circuit switching, in- 
terrupting devices, or both, with buses and connections. 
The assembly may include control and auxiliary devices. Ac- 
cess to the interior of the enclosure is provided by doors, 
removable covers, or both. Metal-enclosed power switchgear 
is available in non-arc-resistant or arc-resistant constructions. 

Motor Control Center. An assembly of one or more en- 
closed sections having a common power bus and princi- 
pally containing motor control units. 

Multioutlet Assembly. A type of surface, flush, or free- 
standing raceway designed to hold conductors and recep- 
tacles, assembled in the field or at the factory. 

Neutral Conductor. The conductor connected to the neu- 
tral point of a system that is intended to carry current under 
normal conditions. 

Neutral Point. The common point on a wye-connection in 
a polyphase system or midpoint on a single-phase, 3-wire 
system, or midpoint of a single-phase portion of a 3-phase 
delta system, or a midpoint of a 3-wire, direct-current system. 

Informational Note: At the neutral point of the system, the 
vectorial sum of the nominal voltages from all other phases 
within the system that utilize the neutral, with respect to the 
neutral point, is zero potential. 

Nonautomatic. Require human intervention to perform a 
function. 

Nonlinear Load. A load where the wave shape of the 
steady-state current does not follow the wave shape of the 
applied voltage. 

Informational Note: Electronic equipment, electronic/electric- 
discharge lighting, adjustable-speed drive systems, and similar 
equipment may be nonlinear loads. 

Outlet. A point on the wiring system at which current is 
taken to supply utilization equipment. 

Outline Lighting. An arrangement of incandescent lamps, 
electric-discharge lighting, or other electrically powered light 
sources to outline or call attention to certain features such as 
the shape of a building or the decoration of a window. 

Overcurrent. Any current in excess of the rated current of 
equipment or the ampacity of a conductor. It may result 
from overload, short circuit, or ground fault. 

Informational Note: A current in excess of rating may be 
accommodated by certain equipment and conductors for a 
given set of conditions. Therefore, the rules for overcurrent 
protection are specific for particular situations. 



70-30 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 100 — DEFINITIONS 



CHAPTER 1 



Overcurrent Protective Device, Branch-Circuit. A de- 
vice capable of providing protection for service, feeder, and 
branch circuits and equipment over the full range of over- 
currents between its rated current and its interrupting rat- 
ing. Branch-circuit overcurrent protective devices are pro- 
vided with interrupting ratings appropriate for the intended 
use but no less than 5000 amperes. 

Overcurrent Protective Device, Supplementary. A de- 
vice intended to provide limited overcurrent protection for 
specific applications and utilization equipment such as lu- 
minaires and appliances. This limited protection is in addi- 
tion to the protection provided in the required branch cir- 
cuit by the branch-circuit overcurrent protective device. 

Overload. Operation of equipment in excess of normal, 
full-load rating, or of a conductor in excess of rated ampac- 
ity that, when it persists for a sufficient length of time, 
would cause damage or dangerous overheating. A fault, 
such as a short circuit or ground fault, is not an overload. 

Panelboard. A single panel or group of panel units de- 
signed for assembly in the form of a single panel, including 
buses and automatic overcurrent devices, and equipped 
with or without switches for the control of light, heat, or 
power circuits; designed to be placed in a cabinet or cutout 
box placed in or against a wall, partition, or other support; 
and accessible only from the front. 

Plenum. A compartment or chamber to which one or more 
air ducts are connected and that forms part of the air distri- 
bution system. 

Power Outlet. An enclosed assembly that may include re- 
ceptacles, circuit breakers, fuseholders, fused switches, 
buses, and watt-hour meter mounting means; intended to 
supply and control power to mobile homes, recreational 
vehicles, park trailers, or boats or to serve as a means for 
distributing power required to operate mobile or tempo- 
rarily installed equipment. 

Premises Wiring (System). Interior and exterior wiring, 
including power, lighting, control, and signal circuit wiring 
together with all their associated hardware, fittings, and 
wiring devices, both permanently and temporarily installed. 
This includes (a) wiring from the service point or power 
source to the outlets or (b) wiring from and including the 
power source to the outlets where there is no service point. 
Such wiring does not include wiring internal to appli- 
ances, luminaires, motors, controllers, motor control cen- 
ters, and similar equipment. 

Qualified Person. One who has skills and knowledge re- 
lated to the construction and operation of the electrical 
equipment and installations and has received safety training 
to recognize and avoid the hazards involved. 



Informational Note: Refer to NFPA 70E-2009, Standard 
for Electrical Safety in the Workplace, for electrical safety 
training requirements. 

Raceway. An enclosed channel of metal or nonmetallic ma- 
terials designed expressly for holding wires, cables, or bus- 
bars, with additional functions as permitted in this Code. 
Raceways include, but are not limited to, rigid metal conduit, 
rigid nonmetallic conduit, intermediate metal conduit, liq- 
uidtight flexible conduit, flexible metallic tubing, flexible 
metal conduit, electrical nonmetallic tubing, electrical metallic 
tubing, underfloor raceways, cellular concrete floor raceways, 
cellular metal floor raceways, surface raceways, wireways, 
and busways. 

Rainproof. Constructed, protected, or treated so as to pre- 
vent rain from interfering with the successful operation of 
the apparatus under specified test conditions. 

Raintight. Constructed or protected so that exposure to a 
beating rain will not result in the entrance of water under 
specified test conditions. 

Receptacle. A receptacle is a contact device installed at the 
outlet for the connection of an attachment plug. A single 
receptacle is a single contact device with no other contact 
device on the same yoke. A multiple receptacle is two or 
more contact devices on the same yoke. 

Receptacle Outlet. An outlet where one or more recep- 
tacles are installed. 

Remote-Control Circuit. Any electrical circuit that controls 
any other circuit through a relay or an equivalent device. 

Sealable Equipment. Equipment enclosed in a case or 
cabinet that is provided with a means of sealing or locking 
so that live parts cannot be made accessible without open- 
ing the enclosure. The equipment may or may not be oper- 
able without opening the enclosure. 

Separately Derived System. A premises wiring system 
whose power is derived from a source of electric energy or 
equipment other than a service. Such systems have no di- 
rect connection from circuit conductors of one system to 
circuit conductors of anothei system, other than connec- 
tions through the earth, metal enclosures, metallic race- 
ways, oi equipment ^'■oiinduiu conductors. 

Service. The conductors and equipment for delivering elec- 
tric energy from the serving utility to the wiring system of 
the premises served. 

Service Cable. Service conductors made up in the form of 
a cable. 

Service Conductors. The conductors from the service point 
to the service disconnecting means. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-31 



CHAPTER 1 



ARTICLE 100 — DEFINITIONS 



Service Conductors, Overhead. The overhead conductors 
between the servi- e point and the first p ji'nl ol connection 
to the sen ice- entrance conductors a! the building qi ofhei 
structure, 

Service Conductors, Underground. Hi undcrgi u d 

conductors between the service joint and the first poin! .,'■ 
connection to the service entrance < onducton in a terminal 
bo? . metf i, oi othei enclosure inside or outside uV builo 
ing wall. 

Informational Note: Where there is no terminal box. 
meter, or oilier enclosure, the poinl of connection is consid- 
ered to be the poini of entrance ol the service conductor! 
into the building. 

Service Drop. The overhe id :onductoi s k tw . en the utility 
''l-.-iifiv supply sj tern and the lervice point 

Service-Entrance Conductors, Overhead System. The 

service conductors between the terminals of the service 
equipment and a point usually outside the building, clear of 
building walls, where joined by tap or splice to the service 

drop or overhead service conductors. 

Service-Entrance Conductors, Underground System. The 

service conductors between the terminals of the service equip- 
ment and the point of connection to the service lateral or 
underground service conductors. 

Informational Note: Where service equipment is located 
outside the building walls, there may be no service- 
entrance conductors or they may be entirely outside the 
building. 

Service Equipment. The necessary equipment, usually con- 
sisting of a circuit breaker(s) or switch(es) and fuse(s) and 
their accessories, connected to the load end of service conduc- 
tors to a building or other structure, or an otherwise designated 
area, and intended to constitute the main control and cutoff of 
the supply. 

Service Lateral. The underground conductors between the 
utility electric supply system and the service point. 

Service Point. The point of connection between the facili- 
ties of the serving utility and the premises wiring. 

Informational Note: Th : sei • ice pini 1 tan Ik described a 
the point ol demarcation between where \h<: serving uutnv 
ends and (lie premises wiring begins The serving utility 
general]) spei if;-, the location oi the service point based 
on the uiiidition , ol service. 

Short-Circuit Current Rating. The prospective symmetri- 
cal fault current at a nominal voltage to which an apparatus 
or system is able to be connected without sustaining dam- 
age exceeding defined acceptance criteria. 

Show Window. Any window used or designed to be used 
for the display of goods or advertising material, whether it 
is fully or partly enclosed or entirely open at the rear and 



whether or not it has a platform raised higher than the street 
floor level. 

Signaling Circuit. Any electrical circuit that energizes sig- 
naling equipment. 

Solar Photovoltaic System. The total components and sub- 
systems that, in combination, convert solar energy into electric 
energy suitable for connection to a utilization load. 

Special Permission. The written consent of the authority 
having jurisdiction. 

Structure. That which is built or constructed. 

Surge Arrester. A protective device for limiting surge volt- 
ages by discharging or bypassing surge current; it also pre- 
vents continued flow of follow current while remaining ca- 
pable of repeating these functions. 

Surge-Protective Device (SPD). A protective device for 
limiting transient voltages by diverting or limiting surge 
current; it also prevents continued flow of follow current 
while remaining capable of repeating these functions and is 
designated as follows: 

Type 1: Permanently connected SPDs intended for instal- 
lation between the secondary of the service transformer and 
the line side of the service disconnect overcurrent device. 

Type 2: Permanently connected SPDs intended for in- 
stallation on the load side of the service disconnect over- 
current device, including SPDs located at the branch panel. 

Type 3: Point of utilization SPDs. 

Type 4: Component SPDs, including discrete compo- 
nents, as well as assemblies. 

Informational Note: For further information on Type 1, 
Type 2, Type 3, and- Type 4 SPDs, see UL 1449, Standard 
for Surge Protective Devices. 

Switch, Bypass Isolation. A manually operated device used 
in conjunction with a transfer switch to provide a means of 
directly connecting load conductors to a power source and of 
disconnecting the transfer switch. 

Switch, General-Use. A switch intended for use in general 
distribution and branch circuits. It is rated in amperes, and 
it is capable of interrupting its rated current at its rated 
voltage. 

Switch, General-Use Snap. A form of general-use switch 
constructed so that it can be installed in device boxes or on 
box covers, or otherwise used in conjunction with wiring 
systems recognized by this Code. 

Switch, Isolating. A switch intended for isolating an elec- 
trical circuit from the source of power. It has no interrupt- 
ing rating, and it is intended to be operated only after the 
circuit has been opened by some other means. 



70-32 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 100 — DEFINITIONS 



CHAPTER 1 



Switch, Motor-Circuit. A switch rated in horsepower that 
is capable of interrupting the maximum operating overload 
current of a motor of the same horsepower rating as the 
switch at the rated voltage. 

Switch, Transfer. An automatic or nonautomatic device for 
transferring one or more load conductor connections from 
one power source to another. 

Switchboard. A large single panel, frame, or assembly of 
panels on which are mounted on the face, back, or both, 
switches, overcurrent and other protective devices, buses, 
and usually instruments. Switchboards are generally acces- 
sible from the rear as well as from the front and are not 
intended to be installed in cabinets. 

Thermal Protector (as applied to motors). A protective 
device for assembly as an integral part of a motor or motor- 
compressor that, when properly applied, protects the motor 
against dangerous overheating due to overload and failure 
to start. 

Informational Note: The thermal protector may consist of 
one or more sensing elements integral with the motor or 
motor-compressor and an external control device. 

Thermally Protected (as applied to motors). The words 
Thermally Protected appearing on the nameplate of a motor 
or motor-compressor indicate that the motor is provided 
with a thermal protector. 

Ungrounded. Not connected to ground or to a conductive 
body that extends the ground connection. 

Unintemiiuti'.j?c V^wi'i* Pdpp'v <\ pov-ci suppl\ used to 

hi i\ >le alternating current | o-.'.or k> i load i.j; some pe.iod 
of time if ihf event ol i po vei lailure. 

Informational Note: In addition it ma} piw de a more 
constant .eii.i"t and frequency supply to the load, reducing 
the effects nl voltage and frequency variations. 

Utility-Interactive Inverter. An inverter intended for use 
in parallel with an electric utility to supply common loads 
that may deliver power to the utility. 

Utilization Equipment. Equipment that utilizes electric en- 
ergy for electronic, electromechanical, chemical, heating, 
lighting, or similar purposes. 

Ventilated. Provided with a means to permit circulation of 
air sufficient to remove an excess of heat, fumes, or vapors. 

Volatile Flammable Liquid. A flammable liquid having a 
flash point below 38°C (100°F), or a flammable liquid 
whose temperature is above its flash point, or a Class II 
combustible liquid that has a vapor pressure not exceeding 
276 kPa (40 psia) at 38°C (100°F) and whose temperature 
is above its flash point. 



Voltage (of a circuit). The greatest root-mean-square (rms) 
(effective) difference of potential between any two conduc- 
tors of the circuit concerned. 

Informational Note: Some systems, such as 3-phase 4-wire, 
single-phase 3-wire, and 3-wire direct current, may have vari- 
ous circuits of various voltages. 

Voltage, Nominal. A nominal value assigned to a circuit or 
system for the purpose of conveniently designating its volt- 
age class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). 
The actual voltage at which a circuit operates can vary from 
the nominal within a range that permits satisfactory opera- 
tion of equipment. 

Informational Note: See ANSI C84. 1-2006, Voltage Rat- 
ings for Electric Power Systems and Equipment (60 Hz). 

Voltage to Ground. For grounded circuits, the voltage be- 
tween the given conductor and that point or conductor of 
the circuit that is grounded; for ungrounded circuits, the 
greatest voltage between the given conductor and any other 
conductor of the circuit. 

Watertight. Constructed so that moisture will not enter the 
enclosure under specified test conditions. 

Weatherproof. Constructed or protected so that exposure 
to the weather will not interfere with successful operation. 

Informational Note: Rainproof, raintight, or watertight equip- 
ment can fulfill the requirements for weatherproof where vary- 
ing weather conditions other than wetness, such as snow, ice, 
dust, or temperature extremes, are not a factor. 



II. Over 600 Volts, Nominal 

Whereas the preceding definitions are intended to apply 
wherever the terms are used throughout this Code, the fol- 
lowing definitions are applicable only to parts of the article 
specifically covering installations and equipment operating 
at over 600 volts, nominal. 

Electronically Actuated Fuse. An overcurrent protective 
device that generally consists of a control module that pro- 
vides current sensing, electronically derived time-current 
characteristics, energy to initiate tripping, and an interrupt- 
ing module that interrupts current when an overcurrent oc- 
curs. Electronically actuated fuses may or may not operate 
in a current-limiting fashion, depending on the type of con- 
trol selected. 

Fuse. An overcurrent protective device with a circuit- 
opening fusible part that is heated and severed by the pas- 
sage of overcurrent through it. 

Informational Note: A fuse comprises all the parts that 
form a unit capable of performing the prescribed functions. 
It may or may not be the complete device necessary to 
connect it into an electrical circuit. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-33 



110.1 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



Controlled Vented Power Fuse. A fuse with provision for 
controlling discharge circuit interruption such that no solid 
material may be exhausted into the surrounding atmosphere. 

Informational Note: The fuse is designed so that dis- 
charged gases will not ignite or damage insulation in the 
path of the discharge or propagate a flashover to or between 
grounded members or conduction members in the path of 
the discharge where the distance between the vent and such 
insulation or conduction members conforms to manufactur- 
er's recommendations. 

Expulsion Fuse Unit (Expulsion Fuse). A vented fuse unit 
in which the expulsion effect of gases produced by the arc 
and lining of the fuseholder, either alone or aided by a 
spring, extinguishes the arc. 

Nonvented Power Fuse. A fuse without intentional provi- 
sion for the escape of arc gases, liquids, or solid particles to 
the atmosphere during circuit interruption. 

Power Fuse Unit. A vented, nonvented, or controlled 
vented fuse unit in which the arc is extinguished by being 
drawn through solid material, granular material, or liquid, 
either alone or aided by a spring. 

Vented Power Fuse. A fuse with provision for the escape 
of arc gases, liquids, or solid particles to the surrounding 
atmosphere during circuit interruption. 

Multiple Fuse. An assembly of two or more single-pole 

fuses. 

Switching Device. A device designed to close, open, or 
both, one or more electrical circuits. 

Circuit Breaker. A switching device capable of making, 
carrying, and interrupting currents under normal circuit 
conditions, and also of making, carrying for a specified 
time, and interrupting currents under specified abnormal 
circuit conditions, such as those of short circuit. 

Cutout. An assembly of a fuse support with either a fuse- 
holder, fuse carrier, or disconnecting blade. The fuseholder 
or fuse carrier may include a conducting element (fuse link) 
or may act as the disconnecting blade by the inclusion of a 
nonfusible member. 

Disconnecting Means. A device, group of devices, or other 
means whereby the conductors of a circuit can be discon- 
nected from their source of supply. 

Disconnecting (or Isolating) Switch (Disconnector, Isola- 
tor). A mechanical switching device used for isolating a 
circuit or equipment from a source of power. 

Interrupter Switch. A switch capable of making, carrying, 
and interrupting specified currents. 

Oil Cutout (Oil-Filled Cutout). A cutout in which all or 
part of the fuse support and its fuse link or disconnecting 
blade is mounted in oil with complete immersion of the 
contacts and the fusible portion of the conducting element 



(fuse link) so that arc interruption by severing of the fuse 
link or by opening of the contacts will occur under oil. 
Oil Switch. A switch having contacts that operate under oil 
(or askarel or other suitable liquid). 

Regulator Bypass Switch. A specific device or combina- 
tion of devices designed to bypass a regulator. 



ARTICLE 110 
Requirements I'nr EfedsicaJ Installations 

I. General 

110.1 Scope. This article covers general requirements for the 
examination and approval, installation and use, access to and 
spaces about electrical conductors and equipment; enclosures 
intended for personnel entry; and tunnel installations. 

110.2 Approval. The conductors and equipment required or 
permitted by this Code shall be acceptable only if approved. 

Informational Note: See 90.7, Examination of Equipment 
for Safety, and 110.3, Examination, Identification, Installa- 
tion, and Use of Equipment. See definitions of Approved, 
Identified, Labeled, and Listed. 

110.3 Examination, Identification, Installation, and Use 
of Equipment. 

(A) Examination. In judging equipment, considerations 
such as the following shall be evaluated: 

(1) Suitability for installation and use in conformity with 
the provisions of this Code 

Informational Note: Suitability of equipment use may be 
identified by a description marked on or provided with a 
product to identify the suitability of the product for a spe- 
cific purpose, environment, or application. Sped.) 1 cniidi 
tions of use or other limitations and other pertinent infoi 
in Lion iii- be rhal > 1 ot. i'w equipment included '< the 
product i istructioris oi m'luA-d at the ipjuopti^n- listing 
and labeling i.iibinunwn. Suitability of equipment may be 
evidenced by listing or labeling. 

(2) Mechanical strength and durability, including, for parts 
designed to enclose and protect other equipment, the 
adequacy of the protection thus provided 

(3) Wire-bending and connection space 

(4) Electrical insulation 

(5) Heating effects under normal conditions of use and also 
under abnormal conditions likely to arise in service 

(6) Arcing effects 

(7) Classification by type, size, voltage, current capacity, 
and specific use 

(8) Other factors that contribute to the practical safeguard- 
ing of persons using or likely to come in contact with 
the equipment 



70-34 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.13 



(B) Installation and Use. Listed or labeled equipment 
shall be installed and used in accordance with any instruc- 
tions included in the listing or labeling. 

110.4 Voltages. Throughout this Code, the voltage consid- 
ered shall be that at which the circuit operates. The voltage 
rating of electrical equipment shall not be less than the 
nominal voltage of a circuit to which it is connected. 

110.5 Conductors. Conductors normally used to carry cur- 
rent shall be of copper unless otherwise provided in this 
Code. Where the conductor material is not specified, the 
material and the sizes given in this Code shall apply to 
copper conductors. Where other materials are used, the size 
shall be changed accordingly. 

Informational Note: For aluminum and copper-clad alumi- 
num conductors, see 310.15. 

110.6 Conductor Sizes. Conductor sizes are expressed in 
American Wire Gage (AWG) or in circular mils. 

110.7 Wiring Integrity. Completed wiring installations 
shall be free from short circuits, ground faults, or any con- 
nections to ground other than as required or permitted else- 
where in this Code. 

110.8 Wiring Methods. Only wiring methods recognized 
as suitable are included in this Code. The recognized meth- 
ods of wiring shall be permitted to be installed in any type 
of building or occupancy, except as otherwise provided in 
this Code. 

110.9 Interrupting Rating. Equipment intended to inter- 
rupt current at fault levels shall have an interrupting rating 
iioi less than the nominal circuit voltage and the current that 
is available at the line terminals of the equipment. 

Equipment intended to interrupt current at other than fault 
levels shall have an interrupting rating at nominal circuit volt- 
age not less than the current that must be interrupted. 

110.10 Circuit Impedance, Short-( ircuit Current tim- 
ings, and Other Characteristics. The overcurrent protec- 
tive devices, the total impedance, the equipment short- 
circuit current ratings, and other characteristics of the 
circuit to be protected shall be selected and coordinated to 
permit the circuit protective devices used to clear a fault to 
do so without extensive damage to the electrical cquiprru i i 
of the circuit. This fault shall be assumed to be either be- 
tween two or more of the circuit conductors or between any 
circuit conductor and the equipment grounding conduc- 
tors) permitted in 250.118. Listed equipment applied in 
accordance with their listing shall be considered to meet the 
requirements of this section. 



110.11 Deteriorating Agents. Unless identified for use in 
the operating environment, no conductors or equipment 
shall be located in damp or wet locations; where exposed to 
gases, fumes, vapors, liquids, or other agents that have a 
deteriorating effect on the conductors or equipment; or 
where exposed to excessive temperatures. 

Informational Note No. 1 : See 300.6 for protection against 
corrosion. 

Informational Note No. 2: Some cleaning and lubricating 
compounds can cause severe deterioration of many plastic 
materials used for insulating and structural applications in 
equipment. 

Equipment not identified for outdoor use and equipment 
identified only for indoor use, such as "dry locations," "in- 
door use only," "damp locations," or enclosure Types 1 , 2, 
5, 12, 12K, and/or 13, shall be protected againsl damage 
from the weather during construction. 

Informational Note No. 3: See Table 1 10.28 for appropriate 
enclosure-type designations. 

110.12 Mechanical Execution of Work. Electrical equip- 
ment shall be installed in a neat and workmanlike manner. 

Informational Note: Accepted industry practices are de- 
scribed in ANSI/NECA 1-2006, Standard Practices for 
Good Workmanship in Electrical Contracting, and other 
ANSI-approved installation standards. 

(A) Unused Openings. Unused openings, other than those 
intended for the operation of equipment, those intended for 
mounting purposes, or those permitted as part of the design 
for listed equipment, shall be closed to afford protection sub- 
stantially equivalent to the wall of the equipment. Where me- 
tallic plugs or plates are used with nonmetallic enclosures, 
they shall be recessed at least 6 mm (14 in.) from the outer 
surface of the enclosure. 

(B) Integrity of Electrical Equipment and Connections. 

Internal parts of electrical equipment, including busbars, 
wiring terminals, insulators, and other surfaces, shall not be 
damaged or contaminated by foreign materials such as 
paint, plaster, cleaners, abrasives, or corrosive residues. 
There shall be no damaged parts that may adversely affect 
safe operation or mechanical strength of the equipment 
such as parts that are broken; bent; cut; or deteriorated by 
corrosion, chemical action, or overheating. 

110.13 Mounting and Cooling of Equipment. 

(A) Mounting. Electrical equipment shall be firmly secured 
to the surface on which it is mounted. Wooden plugs driven 
into holes in masonry, concrete, plaster, or similar materials 
shall not be used. 

(B) Cooling. Electrical equipment that depends on the 
natural circulation of air and convection principles for cool- 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-35 



110.14 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



ing of exposed surfaces shall be installed so that room 
airflow over such surfaces is not prevented by walls or by 
adjacent installed equipment. For equipment designed for 
floor mounting, clearance between top surfaces and adja- 
cent surfaces shall be provided to dissipate rising warm air. 
Electrical equipment provided with ventilating openings 
shall be installed so that walls or other obstructions do not 
prevent the free circulation of air through the equipment. 

110.14 Electrical Connections. Because of different char- 
acteristics of dissimilar metals, devices such as pressure 
terminal or pressure splicing connectors and soldering lugs 
shall be identified for the material of the conductor and 
shall be properly installed and used. Conductors of dissimi- 
lar metals shall not be intermixed in a terminal or splicing 
connector where physical contact occurs between dissimilar 
conductors (such as copper and aluminum, copper and 
copper-clad aluminum, or aluminum and copper-clad alu- 
minum), unless the device is identified for the purpose and 
conditions of use. Materials such as solder, fluxes, inhibi- 
tors, and compounds, where, employed, shall be suitable for 
the use and shall be of a type that will not adversely affect 
the conductors, installation, or equipment. 

Connectors and terminals foi conductors more finely 
stranded than Class B and Class C stranding as shown in 
Chapter 9, Table 10. shall be identified for the specific 
conductor class oi classes. 

Informational Note: Many terminations and equipment are 
marked with a tightening torque. 

(A) Terminals. Connection of conductors to terminal parts 
shall ensure a thoroughly good connection without damaging 
the conductors and shall be made by means of pressure con- 
nectors (including set-screw type), solder lugs, or splices to 
flexible leads. Connection by means of wire-binding screws or 
studs and nuts that have upturned lugs or the equivalent shall 
be permitted for 10 AWG or smaller conductors. 

Terminals for more than one conductor and terminals 
used to connect aluminum shall be so identified. 

(B) Splices. Conductors shall be spliced or joined with 
splicing devices identified for the use or by brazing, weld- 
ing, or soldering with a fusible metal or alloy. Soldered 
splices shall first be spliced or joined so as to be mechani- 
cally and electrically secure without solder and then be 
soldered. All splices and joints and the free ends of conduc- 
tors shall be covered with an insulation equivalent to that of 
the conductors or with an insulating device identified for 
the purpose. 

Wire connectors or splicing means installed on conduc- 
tors for direct burial shall be listed for such use. 

(C) Temperature Limitations. The temperature rating as- 
sociated with the ampacity of a conductor shall be selected 



and coordinated so as not to exceed the lowest temperature 
rating of any connected termination, conductor, or device. 
Conductors with temperature ratings higher than specified 
for terminations shall be permitted to be used for ampacity 
adjustment, correction, or both. 

(1) Equipment Provisions. The determination of termination 
provisions of equipment shall be based on 110.14(C)(1)(a) or 
(C)(1)(b). Unless the equipment is listed and marked other- 
wise, conductor ampacities used in determining equipment ter- 
mination provisions shall be based on Table $10.15i t'»)(16) as 
appropriately modified by 310.15(B)(6). 

(a) Termination provisions of equipment for circuits 
rated 100 amperes or less, or marked for 14 AWG through 
1 AWG conductors, shall be used only for one of the fol- 
lowing: 

(1) Conductors rated 60°C (140°F). 

(2) Conductors with higher temperature ratings, provided 
the ampacity of such conductors is determined based 
on the 60°C (140°F) ampacity of the conductor size 
used. 

(3) Conductors with higher temperature ratings if the equip- 
ment is listed and identified for use with such conductors. 

(4) For motors marked with design letters B, C, or D, con- 
ductors having an insulation rating of 75°C (167°F) or 
higher shall be permitted to be used, provided the am- 
pacity of such conductors does not exceed the 75°C 
(167°F) ampacity. 

(b) Termination provisions of equipment for circuits 
rated over 100 amperes, or marked for conductors larger 
than 1 AWG, shall be used only for one of the following: 

(1) Conductors rated 75°C (167°F) 

(2) Conductors with higher temperature ratings, provided 
the ampacity of such conductors does not exceed the 
75°C (167°F) ampacity of the conductor size used, or 
up to their ampacity if the equipment is listed and iden- 
tified for use with such conductors 

(2) Separate Connector Provisions. Separately installed 
pressure connectors shall be used with conductors at the 
ampacities not exceeding the ampacity at the listed and 
identified temperature rating of the connector. 

Informational Note: With respect to 110.14(C)(1) and 
(C)(2), equipment markings or listing information may ad- 
ditionally restrict the sizing and temperature ratings of con- 
nected conductors. 

110.15 High-Leg Marking. On a 4-wire, delta-connected 
system where the midpoint of one phase winding is 
grounded, only the conductor or busbar having the higher 
phase voltage to ground shall be durably and permanently 
marked by an outer finish that is orange in color or by other 



70-36 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.26 



effective means. Such identification shall be placed at each 
point on the system where a connection is made if the 
grounded conductor is also present. 

110.16 Arc-Flash Hazard Warning. Electrical equipment, 
such as switchboards, panelboards, industrial control pan- 
els, meter socket enclosures, and motor control centers, that 
are in other than dwelling units, and are likely to require 
examination, adjustment, servicing, or maintenance while 
energized shall be field marked to warn qualified persons of 
potential electric arc flash hazards. The marking shall be 
located so as to be clearly visible to qualified persons be- 
fore examination, adjustment, servicing, or maintenance of 
the equipment. 

Informational Note No. 1: NFPA 70E-2009, Standard for 
Electrical Safety in the Workplace, provides assistance in de- 
termining severity of potential exposure, planning safe work 
practices, and selecting personal protective equipment. 

Informational Note No. 2: ANSI Z535.4-1998, Product 
Safety Signs and Labels, provides guidelines for the design 
of safety signs and labels for application to products. 

110.18 Arcing Parts. Parts of electrical equipment that in 
ordinary operation produce arcs, sparks, flames, or molten 
metal shall be enclosed or separated and isolated from all 
combustible material. 

Informational Note: For hazardous (classified) locations, 
see Articles 500 through 517. For motors, see 430.14. 

110.19 Light and Power from Railway Conductors. Cir- 
cuits for lighting and power shall not be connected to any 
system that contains trolley wires with a ground return. 

Exception: Such circuit connections shall be permitted in 
car houses, power houses, or passenger and freight stations 
operated in connection with electric railways. 

110.21 Marking. The manufacturer's name, trademark, or 
other descriptive marking by which the organization re- 
sponsible for the product can be identified shall be placed 
on all electrical equipment. Other markings that indicate 
voltage, current, wattage, or other ratings shall be provided 
as specified elsewhere in this Code. The marking shall be of 
sufficient durability to withstand the environment involved. 

110.22 Identification of Disconnecting Means. 

(A) General. Each disconnecting means shall be legibly 
marked to indicate its purpose unless located and arranged 
so the purpose is evident. The marking shall be of sufficient 
durability to withstand the environment involved. 

(B) Engineered Series Combination Systems. Equipment 
enclosures tor circuit breakers oi h. 1 in compli- 
ance with series combination ratings selected under engi- 



neering supervision in accordance with 240.86(A) shall be 
legibly marked in the field as directed by the engineer to 
indicate the equipment has been applied with a series com- 
bination rating. The marking shall be readily visible and 
state the following: 

CAUTION — ENGINEERED SERIES COMBINA- 
TION SYSTEM RATED AMPERES. IDENTI- 
FIED REPLACEMENT COMPONENTS REQUIRED. 

(C) Tested Series Combination Systems. Equipment en- 
closures for circuit breakers or fuses applied in compliance 
with the series combination ratings marked on the equip- 
ment by the manufacturer in accordance with 240.86(B) shall 
be legibly marked in the field to indicate the equipment has 
been applied with a series combination rating. The marking 
shall be readily visible and state the following: 

CAUTION — SERIES COMBINATION SYSTEM 

RATED AMPERES. IDENTIFIED REPLACEMENT 

COMPONENTS REQUIRED. 

110.23 Current Transformers. Unused current transform- 
ers associated with potentially energized circuits shall be 
short-circuited. 

110.24 Available Fault Current. 

(A) Field Marking. Service equipment in other than 
dwelling units shall be legibly marked in the field with the 
maximum available fault current. The field marking! -o shall 
include the dale the fault curt-iit calculation was performed 
and be ol sufficient durability to withstand the environment 
involved. 

(B) Mt'tfiiiettti'jU^ Whei modifications lo (he electrical 
ui'.tc'H ition oceui that .>ik-il th< rat n.ni i available f-uU 
current at the service, flu" naximufn available molt current 
shall bi verified or recalculated is necessary to ensure the 
service squipment ratings are utfii tent u-i ih maximum 
available fault currenl ai iJv line terminals of the equip- 
ment I'he required field marking(s) in 110.24(A) shall be 
adjusted in reflect the new Lst-I ot iuci\imt'iri a ailable 
faui current 

Exception: The field marking requirements in 110.24(A) 
and 110.24(B) shall not he required in industrial installa- 
tions where condition: <>; maintenance and supervision en- 
sure then on!) qualified persons service the equipment. 

II. 600 Volts, Nominal, or Less 

110.26 Spaces About Electrical Equipment. Access and 
working space shall be provided and maintained about all 
electrical equipment to permit ready and safe operation and 
maintenance of such equipment. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-37 



110.26 



ARTICLE 1 10 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(A) Working Space. Working space for equipment operat- 
ing at 600 volts, nominal, or less to ground and likely to 
require examination, adjustment, servicing, or maintenance 
while energized shall comply with the dimensions of 
110.26(A)(1), (A)(2), and (A)(3) or as required or permitted 
elsewhere in this Code. 

(1) Depth of Working Space. The depth of the working 
space in the direction of live parts shall not be less than that 
specified in Table 110.26(A)(1) unless the requirements of 
110.26(A)(1)(a), (A)(1)(b), or (A)(1)(c) are met. Distances 
shall be measured from the exposed live parts or from the 
enclosure or opening if the live parts are enclosed. 

Table 110.26(A)(1) Working Spaces 



Nominal 

Voltage to 

Ground 


Minimum Clear Distance 


Condition 1 Condition 2 Condition 3 


0-150 
151-600 


914 mm (3 ft) 914 mm (3 ft) 914 mm (3 ft) 

914 mm (3 It) 1.07 m (3 ft 1.22 m (4 ft) 

6 in.) 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side of the working space 

and no live or grounded parts on the other side of the working space, 

or exposed live parts on both sides of the working space that are 

effectively guarded by insulating materials. 

Condition 2 — Exposed live parts on one side of the working space 

and grounded parts on the other side of the working space. Concrete, 

brick, or tile walls shall be considered as grounded. 

Condition 3 — Exposed live parts on both sides of the working 

space. 



(a) Dead-Front Assemblies. Working space shall not be 
required in the back or sides of assemblies, such as dead- 
front switchboards or motor control centers, where all con- 
nections and all renewable or adjustable parts, such as fuses 
or switches, are accessible from locations other than the 
back or sides. Where rear access is required to work on 
nonelectrical parts on the back of enclosed equipment, a 
minimum horizontal working space of 762 mm (30 in.) 
shall be provided. 

(b) Low Voltage. By special permission, smaller work- 
ing spaces shall be permitted where all exposed live parts 
operate at not greater than 30 volts rms, 42 volts peak, or 
60 volts dc. 

(c) Existing Buildings. In existing buildings where electri- 
cal equipment is being replaced, Condition 2 working clear- 
ance shall be permitted between dead-front switchboards, pan- 
elboards, or motor control centers located across the aisle from 
each other where conditions of maintenance and supervision 
ensure that written procedures have been adopted to prohibit 
equipment on both sides of the aisle from being open at the 
same time and qualified persons who are authorized will ser- 
vice the installation. 



(2) Width of Working Space. The width of the working 
space in front of the electrical equipment shall be the width 
of the equipment or 762 mm (30 in.), whichever is greater. 
In all cases, the work space shall permit at least a 90 degree 
opening of equipment doors or hinged panels. 

(3) Height of Working Space. The work space shall be 
clear and extend from the grade, floor, or platform to a height 
of 2.0 m (6V2 ft) or the height of the equipment, whichever is 
greater. Within the height requirements of this section, other 
equipment that is associated with the electrical installation and 
is located above or below the electrical equipment shall be 
permitted to extend not more than 150 mm (6 in.) beyond the 
front of the electrical equipment. 

Exception No. J: In existing dwelling units, seivice equip- 
ment 01 panelboai h that (o n.-t exce v" 2Ql> amp i-'\ shall 
be permitted in spaces where tin height of the working 
space is less than ~'.c> m (6'/?. ft). 

Exception No. 2: Meters that are installed in meter sock- 
ets shall bt pet nun, J to extend beyond the other equip- 
ment. The 'in-;, r socket shall bt required to follow the rules 
ul this section. 

(B) Clear Spaces. Working space required by this section 
shall not be used for storage. When normally enclosed live 
parts are exposed for inspection or servicing, the working 
space, if in a passageway or general open space, shall be 
suitably guarded. 

(C) Entrance to and Egress from Working Space. 

(1) Minimum Required. At least one entrance of suffi- 
cient area shall be provided to give access to and egress 
from working space about electrical equipment. 

(2) Large Equipment. For equipment rated 1200 amperes 
or more and over 1.8 m (6 ft) wide that contains overcur- 
rent devices, switching devices, or control devices, there 
shall be one entrance to and egress from the required work- 
ing space not less than 610 mm (24 in.) wide and 2.0 m 
(6V2 ft) high at each end of the working space. 

A single entrance to and egress from the required work- 
ing space shall be permitted where either of the conditions 
in 110.26(C)(2)(a) or (C)(2)(b) is met. 

(a) Unobstructed Egress. Where the location permits a 
continuous and unobstructed way of egress travel, a single 
entrance to the working space shall be permitted. 

(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.26(A)(1), a 
single entrance shall be permitted. It shall be located such 
that the distance from the equipment to the nearest edge of 
the entrance is not less than the minimum clear distance 
specified in Table 110.26(A)(1) for equipment operating at 
that voltage and in that condition. 



70-38 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.28 



(3) Personnel Doors. Where equipment rated 1200 A or 
more that contains overcurrent devices, switching devices, 
or control devices is installed and there is a personnel 
door(s) intended for entrance to and egress from the work- 
ing space less than 7.6 m (25 ft) from the nearest edge of 
the working space, the door(s) shall open in the direction of 
egress and be equipped with panic bars, pressure plates, or 
other devices that are normally latched but open under 
simple pressure. 

(D) Illumination. Illumination shall be provided for all 
working spaces about service equipment, switchboards, 
panelboards, or motor control centers installed indoors and 
shall not be controlled ty iiitomatic means only. Additional 
lighting outlets shall not be required where the work space 
is illuminated by an adjacent light source or as permitted by 
210.70(A)(1), Exception No. 1, for switched receptacles. 

(E) Dedicated Equipment Space. All switchboards, pan- 
elboards, and motor control centers shall be located in dedi- 
cated spaces and protected from damage. 

Exception: Control equipment that by its very nature or 
because of other rules of the Code must be adjacent to or 
within sight of its operating machinery shall be permitted 
in those locations. 

(1) Indoor. Indoor installations shall comply with 
110.26(E)(1)(a) through (E)(1)(d). 

(a) Dedicated Electrical Space. The space equal to the 
width and depth of the equipment and extending from the 
floor to a height of 1.8 m (6 ft) above the equipment or to 
the structural ceiling, whichever is lower, shall be dedicated 
to the electrical installation. No piping, ducts, leak protec- 
tion apparatus, or other equipment foreign to the electrical 
installation shall be located in this zone. 

Exception: Suspended ceilings with removable panels shall 
be permitted within the 1.8-m (6-ft) zone. 

(b) Foreign Systems. The area above the dedicated 
space required by 110.26(E)(1)(a) shall be permitted to 
contain foreign systems, provided protection is installed to 
avoid damage to the electrical equipment from condensa- 
tion, leaks, or breaks in such foreign systems. 

(c) Sprinkler Protection. Sprinkler protection shall be 
permitted for the dedicated space where the piping com- 
plies with this section. 

(d) Suspended Ceilings. A dropped, suspended, or 
similar ceiling that does not add strength to the building 
structure shall not be considered a structural ceiling. 

(2) Outdoor. Outdoor electrical equipment shall be in- 
stalled in suitable enclosures and shall be protected from 
accidental contact by unauthorized personnel, or by vehicu- 
lar traffic, or by accidental spillage or leakage from piping 
systems. The working clearance space shall include the 



zone described in 110.26(A). No architectural appurtenance 
or other equipment shall be located in this zone. 

(F) Locked Electrical Equipment Rooms or Enclosures. 

Electrical equipment rooms or enclosures housing electrical 
apparatus that are controlled by a lock(s) shall be consid- 
ered accessible to qualified persons. 

110.27 Guarding of Live Parts. 

(A) Live Parts Guarded Against Accidental Contact. 

Except as elsewhere required or permitted by this Code, 
live parts of electrical equipment operating at 50 volts or 
more shall be guarded against accidental contact by ap- 
proved enclosures or by any of the following means: 

(1) By location in a room, vault, or similar enclosure that is 
accessible only to qualified persons. 

(2) By suitable permanent, substantial partitions or screens 
arranged so that only qualified persons have access to 
the space within reach of the live parts. Any openings 
in such partitions or screens shall be sized and located 
so that persons are not likely to come into accidental 
contact with the live parts or to bring conducting ob- 
jects into contact with them. 

(3) By location on a suitable balcony, gallery, or plat- 
form elevated and arranged so as to exclude unquali- 
fied persons. 

(4) By elevation of 2.5 m (8 ft) or more above the floor or 
other working surface. 

(B) Prevent Physical Damage. In locations where electri- 
cal equipment is likely to be exposed to physical damage, 
enclosures or guards shall be so arranged and of such 
strength as to prevent such damage. 

(C) Warning Signs. Entrances to rooms and other guarded 
locations that contain exposed live parts shall be marked 
with conspicuous warning signs forbidding unqualified per- 
sons to enter. 

Informational Note: For motors, see 430.232 and 430.233. 
For over 600 volts, see 110.34. 

110.28 Enclosure Types. Enclosures (other than surround- 
ing fences or walls) of switchboards, panelboards, indus- 
trial control panels, motor control centers, meter sockets, 
enclosed switches, transfei switches, power outlets, circuit 
breal ers, ldjustabk speed drive r> items, pullout switches. 
portable power distribution equipment, termination 
boxes gi neral purpose tran formers, fire pump control- 
lers, fire pump motors, and motor controllers, rated not 
over 600 volts nominal and intended for such locations, 
shall be marked with an enclosure-type number as shown 
in Table 110.28. 

Table 110.28 shall be used for selecting these enclo- 
sures for use in specific locations other than hazardous 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-39 



110.30 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(classified) locations. The enclosures are not intended to 
protect against conditions such as condensation, icing, cor- 
rosion, or contamination that may occur within the enclo- 
sure or enter via the conduit or unsealed openings. 

III. Over 600 Volts, Nominal 

110.30 General. Conductors and equipment used on cir- 
cuits over 600 volts, nominal, shall comply with Part I of 
this article and with 110.30 through 110.40, which supple- 
ment or modify Part I. In no case shall the provisions of 
this part apply to equipment on the supply side of the ser- 
vice point. 

110.31 Enclosure for Electrical Installations. Electrical 
installations in a vault, room, or closet or in an area sur- 
rounded by a wall, screen, or fence, access to which is 
controlled by a lock(s) or other approved means, shall be 
considered to be accessible to qualified persons only. The 
type of enclosure used in a given case shall be designed and 
constructed according to the nature and degree of the haz- 
ard^) associated with the installation. 

For installations other than equipment as described in 
110.31(D), a wall, screen, or fence shall be used to enclose 
an outdoor electrical installation to deter access by persons 
who are not qualified. A fence shall not be less than 2.1 m 
(7 ft) in height or a combination of 1 .8 m (6 ft) or more of 
fence fabric and a 300-mm ( 1 -ft) or more extension utiliz- 
ing three or more strands of barbed wire or equivalent. The 
distance from the fence to live parts shall be not less than 
given in Table 110.31. 

Table 110.31 Minimum Distance from Fence to Live Parts 





Minimum Distance to Live Parts 


Nominal Voltage 


m ft 


601 - 13,799 

13,800- 230,000 

Over 230,000 


3.05 10 
4.57 15 
5.49 18 



Note: For clearances of conductors for specific system voltages and 
typical BIL ratings, see ANSI C2-2007, National Electrical Safety 
Code. 



Informational Note: See Article 450 for construction re- 
quirements for transformer vaults. 

(A) Electrical Vaults. Where an e.k ctrical vault is required 
or specified for conductors and equipment operating at over 
600 volts, nominal, the following shall .- pply. 

(1) Walls and Roof. The walls and roof shall be con- 
structed of materials that have adequate structural strength 
for the conditions, with a minimum fire rating of 3 hours. 



For the purpose of this section, studs and wuliboard con- 
struction shall not be permitted. 

(2) Floors. The floors of vaults in contact with the earth 
shall be of concrete that is not less than 102 mm (4 in.) 
thick, but where the vault is constructed with a vacant 
space or other stories below it, the floor shall have adequate 
structural strength for the load imposed on it and a mini- 
mum fire resistance of 3 hours. 

(3) Doors. Each doorway leading into a vauli from the 
building interior shall be provided with a tig) t titling door 
that has a minimum fire rating of J Injurs. The authority 
having jurisdiction shall be permitted to require such a door 
for an exterior wall opening where conditions warrant, 

ExceptU n to (I), (2), and ( J) Where -he vui>'j is pro- 
tected with automatic sprinkler, watci spray carbon diox- 
ide, or halon, construction with c I hour rating shall be 
permitted. 

(4) Locks. Doors shall be equipped with locks, and doors 
shall be kept lo.-ked. with access allowed only w .]"iJii<ed 
persons Personnel doors shall swing out and be equipped 
with panic bars, pressure plates, or other devices that are 
normally latched but that open under simple pressure. 

(5) TriHisFw-Hiers. Where a transformer is installed in a 
vault as required by Article 450, the vault shair be con- 
structed in accordance with the reqi'iivnienis of Pari III of 
Article 450. 

Informational Note No. 1 : For additional information, see 
ANSI/ASTM El 19-1995, Method j >i i ire Tests <;/ Building 
Construction and Materials. NFP^ 151 2006,' Standard 
Methods of Tests oj Fin Resistance of Building Constrm 
Hon and Materials, and NFPA 80-2010 Standard foi Fin 
Doors and Other Opening Protectives. 

Informational Note No. 2: A typical 3-hour construction is 
150 mm (6 in.) thick reinforced concrete; 

(B) Indoor Installations. 

(1) In Places Accessible to Unqualified Persons. Indoor 
electrical installations that are accessible to unqualified 
persons shall be made with metal-enclosed equipment. 
Metal-enclosed switchgear, unit substations, transform- 
ers, pull boxes, connection boxes, and other similar as- 
sociated equipment shall be marked with appropriate 
caution signs. Openings in ventilated dry-type transform- 
ers or similar openings in other equipment shall be de- 
signed so that foreign objects inserted through these 
openings are deflected from energized parts. 

(2) In Places Accessible to Qualified Persons Only. In- 
door electrical installations considered accessible only to 
qualified persons in accordance with this section shall com- 
ply with 110.34, 110.36, and 490.24. 



70-40 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.31 



Table 110.28 Enclosure Selection 



For Outdoor Use 



Provides a Degree of 

Protection Against the 

Following Environmental 

Conditions 



Enclosure-Type Number 



3R 



3S 



3X 



3RX 



3SX 



4X 



6P 



Incidental contact with the 
enclosed equipment 

Rain, snow, and sleet 

Sleet* 

Windblown dust 

Hosedown 

Corrosive agents 

Temporary submersion 

Prolonged submersion 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 
X 
X X 

— X 



X 



X 



X 


X 


X 


X 


X 


X 


— 


— 


— 


— 


X 


X 


X 


X 


X 


— 


X 


X 


X 


X 


X 


— 


X 


— 


X 


— 


— 


— 


X 


X 




_ 


_ 


_ 


X 



Provides a Degree of 
Protection Against the 
Following Environmental 
Conditions 



For Indoor Use 



Enclosure-Type Number 



4X 



6P 



12 12K 



13 



Incidental contact with the 
enclosed equipment 

Falling dirt 

Falling liquids and light 
splashing 

Circulating dust, lint, fibers, 
and flyings 

Settling airborne dust, lint, 
fibers, and flyings 

Hosedown and splashing 
water 

Oil and coolant seepage 

Oil or coolant spraying and 
splashing 

Corrosive agents 

Temporary submersion 

Prolonged submersion 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 



X 
X 
X 



X 



X 



X 



X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 



X 



X 



X 
X 



*Mechanism shall be operable when ice covered. 

Informational Note No. 1: The term raintight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6R The term 

rainproof is typically used in conjunction with Enclosure Types 3R, and 3RX. The term watertight is typically used in conjunction with Enclosure 

Types 4, 4X, 6, 6P. The term driptight is typically used in conjunction with Enclosure Types 2, 5, 12, 12K, and 13. The term dusttight is typically 

used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 5, 12, 12K, and 13. 

Informational Note No >: Ingress protection il > i < iil may b< ound in ANSl/NEMA 60529. Degrees of Prot ,*',•<> » vided bx Enclosures. IP 

rati is . are ivs j ;iib titiite for i'uJ > ure T>,*" i 'tings 



201 1 Edition NATIONAL ELECTRICAL CODE 



70-41 



110.32 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(C) Outdoor Installations. 

(1) In Places Accessible to Unqualified Persons. Outdoor 
electrical installations that are open to unqualified persons 
shall comply with Parts I, II, and III of Article 225. 

(2) In Places Accessible to Qualified Persons Only. Out- 
door electrical installations that have exposed live parts 
shall be accessible to qualified persons only in accordance 
with the first paragraph of this section and shall comply 
with 110.34, 110.36, and 490.24. 

(D) Enclosed Equipment Accessible to Unqualified Per- 
sons. Ventilating or similar openings in equipment shall be 
designed such that foreign objects inserted through these 
openings are deflected from energized parts. Where ex- 
posed to physical damage from vehicular traffic, suitable 
guards shall be provided. Nonmetallic or metal-enclosed 
equipment located outdoors and accessible to the general 
public shall be designed such that exposed nuts or bolts 
cannot be readily removed, permitting access to live parts. 
Where nonmetallic or metal-enclosed equipment is acces- 
sible to the general public and the bottom of the enclosure 
is less than 2.5 m (8 ft) above the floor or grade level, the 
enclosure door or hinged cover shall be kept locked. Doors 
and covers of enclosures used solely as pull boxes, splice 
boxes, or junction boxes shall be locked, bolted, or 
screwed on. Underground box covers that weigh over 
45.4 kg (100 lb) shall be considered as meeting this 
requirement. 

110.32 Work Space About Equipment. Sufficient space 
shall be provided and maintained about electrical equip- 
ment to permit ready and safe operation and maintenance 
of such equipment. Where energized parts are exposed, 
the minimum clear work space shall be not less than 
2.0 m (6'/2 ft) high (measured vertically from the floor or 
platform) or not less than 914 mm (3 ft) wide (measured 
parallel to the equipment). The depth shall be as required 
in 110.34(A). In all cases, the work space shall permit at 
least a 90 degree opening of doors or hinged panels. 

110.33 Entrance to Enclosures and Access to Working 
Space. 

(A) Entrance. At least one entrance to enclosures for elec- 
trical installations as described in 110.31 not less than 
610 mm (24 in.) wide and 2.0 m (6V2 ft) high shall be 
provided to give access to the working space about electri- 
cal equipment. 

(1) Large Equipment. On switchboard and control panels 
exceeding 1.8 m (6 ft) in width, there shall be one entrance 
at each end of the equipment. A single entrance to the 
required working space shall be permitted where either of 
the conditions in 110.33(A)(1)(a) or (A)(1)(b) is met. 



(a) Unobstructed Exit. Where the location permits a 
continuous and unobstructed way of exit travel, a single 
entrance to the working space shall be permitted. 

(b) Extra Working Space. Where the depth of the 
working space is twice that required by 110.34(A), a single 
entrance shall be permitted. It shall be located so that the 
distance from the equipment to the nearest edge of the 
entrance is not less than the minimum clear distance speci- 
fied in Table 110.34(A) for equipment operating at that 
voltage and in that condition. 

(2) Guarding. Where bare energized parts at any voltage 
or insulated energized parts above 600 volts, nominal, to 
ground are located adjacent to such entrance, they shall be 
suitably guarded. 

(3) Personnel Doors. Where there is a personnel door(s) 
intended for entrance to and egress from the working space 
less than 7.6 m (25 ft) from the nearest edge of the working 
space, the door(s) shall open in the direction of egress and be 
equipped with panic bars, pressure plates, or other devices that 
are normally latched but open under simple pressure. 

(B) Access. Permanent ladders or stairways shall be pro- 
vided to give safe access to the working space around elec- 
trical equipment installed on platforms, balconies, or mez- 
zanine floors or in attic or roof rooms or spaces. 

110.34 Work Space and Guarding. 

(A) Working Space. Except as elsewhere required or per- 
mitted in this Code, equipment likely to require examina- 
tion, adjustment, servicing, or maintenance while energized 
shall have clear working space in the direction of access to 
live parts of the electrical equipment and shall be not less 
than specified in Table 110.34(A). Distances shall be mea- 
sured from the live parts, if such are exposed, or from the 
enclosure front or opening if such are enclosed. 

Exception: Working space shall not be required in back of 
equipment such as dead-front switchboards or control as- 
semblies where there are no renewable or adjustable parts 
(such as fuses or switches) on the back and where all con- 
nections are accessible from locations other than the back. 
Where rear access is required to work on nonel 'c trical 
parts on the back of enclosed equipment, a minimum work- 
ing space of 762 mm (30 in.) horizontally shall be provided. 

(B) Separation from Low-Voltage Equipment. Where 
switches, cutouts, or other equipment operating at 600 
volts, nominal, or less are installed in a vault, room, or 
enclosure where there are exposed live parts or exposed 
wiring operating at over 600 volts, nominal, the high- 
voltage equipment shall be effectively separated from the 
space occupied by the low-voltage equipment by a suitable 
partition, fence, or screen. 



70-42 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 1 10 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.51 



Table 110.34(A) Minimum Depth of Clear Working Space at 
Electrical Equipment 



Table 110.34(E) Elevation of Unguarded Live Parts Above 
Working Space 



Nominal 

Voltage 

to Ground 


Minimum Clear Distance 


Nomina! Voltage 
Between Phases 


Elevation 


i 


Condition 1 


Condition 2 


Condition 3 


m 


ft 


601-2500 V 

2501-9000 V 

9001-25,000 V 

25,001 V-75 kV 

Above 75 kV 


900 mm (3 ft) 
1.2 m (4 ft) 
1 .5 m (5 ft) 
1.8 m (6 ft) 
2.5 m (8 ft) 


1.2 m (4 ft) 
1 .5 m (5 ft) 
1.8 m (6 ft) 
2.5 m (8 ft) 
3.0 m (10 ft) 


1.5 m (5 ft) 
1.8 m (6 ft) 
2.8 m (9 ft) 
3.0 m (10 ft) 

3.7 m (12 ft) 


601-7500 V 

7501-35,000 V 

Over 35 kV 


2.8 

2.9 

2.9 m + 9.5 mm/kV 

above 35 


9 

9 ft 6 in. 
9 ft 6 in. + 
0.37 in./kV 

above 35 



Note: Where the conditions are as follows: 

Condition 1 — Exposed live parts on one side of the working space 

and no live or grounded parts on the other side of the working space, 

or exposed live parts on both sides of the working space that are 

effectively guarded by insulating materials. 

Condition 2 — Exposed live parts on one side of the working space 

and grounded parts on the other side of the working space. Concrete, 

brick, or tile walls shall be considered as grounded. 

Condition 3 — Exposed live parts on both sides of the working 

space. 



Exception: Switches or other equipment operating at 600 
volts, nominal, or less and serving only equipment within 
the high-voltage vault, room, or enclosure shall be permit- 
ted to be installed in the high-voltage vault, room, or en- 
closure without a partition, fence, or screen if accessible to 
qualified persons only. 

(C) Locked Rooms or Enclosures. The entrance to all 
buildings, vaults, rooms, or enclosures containing exposed 
live parts or exposed conductors operating at over 600 
volts, nominal, shall be kept locked unless such entrances 
are under the observation of a qualified person at all times. 

Where the voltage exceeds 600 volts, nominal, perma- 
nent and conspicuous warning signs shall be provided, 
reading as follows: 

DANGER — HIGH VOLTAGE — KEEP OUT 

(D) Illumination. Illumination shall be provided for all 
working spaces about electrical equipment. The lighting 
outlets shall be arranged so that persons changing lamps or 
making repairs on the lighting system are not endangered 
by live parts or other equipment. 

The points of control shall be located so that persons 
are not likely to come in contact with any live part or 
moving part of the equipment while turning on the lights. 

(E) Elevation of Unguarded Live Parts. Unguarded live 
parts above working space shall be maintained at elevations 
not less than required by Table 110.34(E). 

(F) Protection of Service Equipment, Metal-Enclosed 
Power Switchgear, and Industrial Control Assemblies. 

Pipes or ducts foreign to the electrical installation and re- 
quiring periodic maintenance or whose malfunction would 



endanger the operation of the electrical system shall not be 
located in the vicinity of the service equipment, metal- 
enclosed power switchgear, or industrial control assemblies. 
Protection shall be provided where necessary to avoid damage 
from condensation leaks and breaks in such foreign systems. 
Piping and other facilities shall not be considered foreign if 
provided for fire protection of the electrical installation. 

110.36 Circuit Conductors. Circuit conductors shall be per- 
mitted to be installed in raceways; in cable trays; as metal-clad 
cable, as bare wire, cable, and busbars; or as Type MV cables 
or conductors as provided in 300.37, 300.39, 300.40, and 
300.50. Bare live conductors shall comply with 490.24. 

Insulators, together with their mounting and conductor at- 
tachments, where used as supports for wires, single-conductor 
cables, or busbars, shall be capable of safely withstanding the 
maximum magnetic forces that would prevail if two or more 
conductors of a circuit were subjected to short-circuit current. 

Exposed runs of insulated wires and cables that have a 
bare lead sheath or a braided outer covering shall be sup- 
ported in a manner designed to prevent physical damage to 
the braid or sheath. Supports for lead-covered cables shall 
be designed to prevent electrolysis of the sheath. 

110.40 Temperature Limitations at Terminations. Con- 
ductors shall be permitted to be terminated based on the 
90°C (194°F) temperature rating and ampacity as given in 
Table 310.60(0(67) through Table 310.60(0(86), unless 
otherwise identified. 

IV. Tunnel Installations over 600 Volts, Nominal 

110.51 General. 

(A) Covered. The provisions of this part shall apply to the 
installation and use of high-voltage power distribution and 
utilization equipment that is portable, mobile, or both, such 
as substations, trailers, cars, mobile shovels, draglines, 
hoists, drills, dredges, compressors, pumps, conveyors, un- 
derground excavators, and the like. 



2011 Edition NATIONAL ELECTRICAL CODE 



70-43 



110.52 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



(B) Other Articles. The requirements of this part shall be 
additional to, or amendatory of, those prescribed in Articles 
100 through 490 of this Code. 

(C) Protection Against Physical Damage. Conductors 
and cables in tunnels shall be located above the tunnel floor 
and so placed or guarded to protect them from physical 
damage. 

110.52 Overcurrent Protection. Motor-operated equip- 
ment shall be protected from overcurrent in accordance 
with Parts III, IV, and V of Article 430. Transformers shall 
be protected from overcurrent in accordance with 450.3. 

110.53 Conductors. High-voltage conductors in tunnels 
shall be installed in metal conduit or other metal raceway, 
Type MC cable, or other approved multiconductor cable. 
Multiconductor portable cable shall be permitted to supply 
mobile equipment. 

110.54 Bonding and Equipment Grounding Conductors. 

(A) Grounded and Bonded. All non-current-carrying 
metal parts of electrical equipment and all metal raceways 
and cable sheaths shall be solidly grounded and bonded to 
all metal pipes and rails at the portal and at intervals not 
exceeding 300 m (1000 ft) throughout the tunnel. 

(B) Equipment Grounding Conductors. An equipment 
grounding conductor shall be run with circuit conductors 
inside the metal raceway or inside the multiconductor cable 
jacket. The equipment grounding conductor shall be per- 
mitted to be insulated or bare. 

110.55 Transformers, Switches, and Electrical Equip- 
ment. All transformers, switches, motor controllers, mo- 
tors, rectifiers, and other equipment installed belowground 
shall be protected from physical damage by location or 
guarding. 

110.56 Energized Parts. Bare terminals of transformers, 
switches, motor controllers, and other equipment shall be 
enclosed to prevent accidental contact with energized parts. 

110.57 Ventilation System Controls. Electrical controls for 
the ventilation system shall be arranged so that the airflow can 
be reversed. 

110.58 Disconnecting Means. A switch or circuit breaker 
that simultaneously opens all ungrounded conductors of the 
circuit shall be installed within sight of each transformer or 
motor location for disconnecting the transformer or motor. 
The switch or circuit breaker for a transformer shall have 
an ampere rating not less than the ampacity of the trans- 
former supply conductors. The switch or circuit breaker for 



a motor shall comply with the applicable requirements of 
Article 430. 

110.59 Enclosures. Enclosures for use in tunnels shall be 
dripproof, weatherproof, or submersible as required by the 
environmental conditions. Switch or contactor enclosures 
shall not be used as junction boxes or as raceways for 
conductors feeding through or tapping off to other switches, 
unless the enclosures comply with 312.8. 

V. Manholes and Other Electrical Enclosures Intended 
for Personnel Entry, All Voltages 

110.70 General. Electrical enclosures intended for person- 
nel entry and specifically fabricated for this purpose shall 
be of sufficient size to provide safe work space about elec- 
trical equipment with live parts that is likely to require 
examination, adjustment, servicing, or maintenance while 
energized. Such enclosures shall have sufficient size to per- 
mit ready installation or withdrawal of the conductors em- 
ployed without damage to the conductors or to their insu- 
lation. They shall comply with the provisions of this part. 

Exception: Where electrical enclosures covered by Part V 
of this article are part of an industrial wiring system oper- 
ating under conditions of maintenance and supervision that 
ensure that only qualified persons monitor and supervise 
the system, they shall be permitted to be designed and in- 
stalled in accordance with appropriate engineering prac- 
tice. If required by the authority having jurisdiction, design 
documentation shall be provided. 

110.71 Strength. Manholes, vaults, and their means of ac- 
cess shall be designed under qualified engineering supervi- 
sion and shall withstand all loads likely to be imposed on 
the structures. 

Informational Note: See ANSI C2-2007, National Electri- 
cal Safety Code, for additional information on the loading 
that can be expected to bear on underground enclosures. 

110.72 Cabling Work Space. A clear work space not less 
than 900 mm (3 ft) wide shall be provided where cables are 
located on both sides, and not less than 750 mm (2'/2 ft) 
where cables are only on one side. The vertical headroom 
shall be not less than 1.8 m (6 ft) unless the opening is 
within 300 mm (1 ft), measured horizontally, of the adja- 
cent interior side wall of the enclosure. 

Exception: A manhole containing only one or more of the 
following shall be permitted to have one of the horizontal 
work space dimensions reduced to 600 mm (2 ft) where the 
other horizontal clear work space is increased so the sum 
of the two dimensions is not less than 1.8 in (6 ft): 

(1) Optical fiber cables as covered in Article 770 



70-44 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 110 — REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 



110.79 



(2) Power-limited fire alarm circuits supplied in accor- 
dance with 760.121 

(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.121 

110.73 Equipment Work Space. Where electrical equip- 
ment with live parts that is likely to require examination, 
adjustment, servicing, or maintenance while energized is 
installed in a manhole, vault, or other enclosure designed 
for personnel access, the work space and associated re- 
quirements in 110.26 shall be met for installations operat- 
ing at 600 volts or less. Where the installation is over 
600 volts, the work space and associated requirements in 
110.34 shall be met. A manhole access cover that weighs 
over 45 kg (100 lb) shall be considered as meeting the 
requirements of 110.34(C). 

110.74 Con«1iKu>' ?!i£>talla."s.*n. Conductors installed in 

manholes and other ertclosures iii<cn>ie<i forpe smuit» entrj 
sh-dl be cabled, racked up oi arranged in an . pptovru 
inannei thai provides ready an-i safe acces »» persons to 
cn'.e- foi inMallO'ioii dt>d maintenance The in: !: Ilaiion shall 
• i riply with ll 0.74(A) 01 110 1(B) ■< applicable 

(A) 600 Volts, Nominal, in' Less. Wire bending space for 
conductors operating at 600 volts or less shall be provided 
in accordance with the requirements of ^ (4.28. 

(B) Ovt^r ttiji! \oits, Nqmtosu Coum' tors operatin; t" 
over 6(50 vuli-. shall Ik provided with beading --.pace in 
accordance with 314.71(A) and (Bi, as Applicable. 

Exception: Where 314.71(B) applies, each row or column 
of ducts on one wall of the enclosure shall be calculated 
individually, and the single row or column that provides the 
maximum distance shall be used. 

110.75 Access to Manholes. 

(A) Dimensions. Rectangular access openings shall not be 
less than 650 mm x 550 mm (26 in. x 22 in.). Round access 
openings in a manhole shall be not less than 650 mm 
(26 in.) in diameter. 

Exception: A manhole that has a fixed ladder that does not 
obstruct the opening or that contains only one or more of 
the following shall be permitted to reduce the minimum 
cover diameter to 600 mm (2 ft): 

(1) Optical fiber cables as covered in Article 770 

(2) Power-limited fire alarm circuits supplied in accor- 
dance with 760.121 



(3) Class 2 or Class 3 remote-control and signaling cir- 
cuits, or both, supplied in accordance with 725.121 

(B) Obstructions. Manhole openings shall be free of pro- 
trusions that could injure personnel or prevent ready egress. 

(C) Location. Manhole openings for personnel shall be 
located where they are not directly above electrical equip- 
ment or conductors in the enclosure. Where this is not prac- 
ticable, either a protective barrier or a fixed ladder shall be 
provided. 

(D) Covers. Covers shall be over 45 kg (100 lb) or other- 
wise designed to require the use of tools to open. They shall 
be designed or restrained so they cannot fall into the man- 
hole or protrude sufficiently to contact electrical conductors 
or equipment within the manhole. 

(E) Marking. Manhole covers shall have an identifying 
mark or logo that prominently indicates their function, such 
as "electric." 

110.76 Access to Vaults and Ttannels. 

(A) Location. Access openings for personnel shall be lo- 
cated where they are not directly above electrical equip- 
ment or conductors in the enclosure. Other openings shall 
be permitted over equipment to facilitate installation, main- 
tenance, or replacement of equipment. 

(B) Locks. In addition to compliance with the requirements 
of 110.34, if applicable, access openings for personnel shall 
be arranged such that a person on the inside can exit when 
the access door is locked from the outside, or in the case of 
normally locking by padlock, the locking arrangement shall 
be such that the padlock can be closed on the locking sys- 
tem to prevent locking from the outside. 

110.77 Ventilation. Where manholes, tunnels, and vaults 
have communicating openings into enclosed areas used by 
the public, ventilation to open air shall be provided wher- 
ever practicable. 

110.78 Guarding. Where conductors or equipment, or 
both, could be contacted by objects falling or being pushed 
through a ventilating grating, both conductors and live parts 
shall be protected in accordance with the requirements of 
110.27(A)(2) or 110.31(B)(1), depending on the voltage. 

110.79 Fixed Ladders. Fixed ladders shall be corrosion 
resistant. 



2011 Edition NATIONAL ELECTRICAL CODE 



70-45 



CHAPTER 2 



ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



Chapter 2 Wiring and Protection 



ARTICLE 200 

Use and Identification of Grounded 
■ ■. Conductors - ■ 

200.1 Scope. This article provides requirements for the 
following: 

(1) Identification of terminals 

(2) Grounded conductors in premises wiring systems 

(3) Identification of grounded conductors 

Informational Note: See Article 100 for definitions of 
Grounded Conductor, Equipment Grounding Conductor, 
and Grounding Electrode Conductor, 

200.2 General. Grounded conductors shall comply with 
200.2(A) and (B). 

(A) Insulation. The grounded conductor, where insulated, 
shall have insulation that is (1) suitable, other than color, 
for any ungrounded conductor of the same circuit on cir- 
cuits of less than 1000 volts or impedance grounded neutral 
systems of 1 kV and over, or (2) rated not less than 
600 volts for solidly grounded neutral systems of 1 kV and 
over as described in 250.184(A). 

(B) Continuity. The continuity of a grounded conductor 
shall not depend on a connection to a metallic enclosure, 
raceway, or cable armor. 

Informational Note: See 300.13(B) foi the continuity of 
grounded con lu t irs us< d in mi'ln * in \ ranch cin i'if' 

200.3 Connection to Grounded System. Premises wiring 
shall not be electrically connected to a supply system unless 
the latter contains, for any grounded conductor of the interior 
system, a corresponding conductor that is grounded. For the 
purpose of this section, electrically connected shall mean con- 
nected so as to be capable of carrying current, as distinguished 
from connection through electromagnetic induction. 

Exception: Listed utility-interactive inverters identified for 
use in distributed resource generation systems such as pho- 
tovoltaic and fuel cell power systems shall be permitted to 
be connected to premises wiring without a grounded con- 
ductor where the connected premises wiring or utility sys- 
tem includes a grounded conductor. 

200.4 Neutral Conductors. Neutral conductor:-; shall not 
be used for more than one branch circuit, for more than one 
muliiwin branch circuit, oi for more thi.i one set of un 



jrtj.u.'Kl feedei conductors in, 1 -"- specifically pc-nuiir-i 
elsewhere in this Code. 

200.6 Means of Identifying Grounded Conductors. 

(A) Sizes 6 AWG or Smaller. An insulated grounded con- 
ductor of 6 AWG or smaller shall be identified by one of 
the following means: 

(1) A continuous white out ei finish 

(2) A continuous gray outer finish. 

(3) Thi v continuou whits stripes along the conductor's 
enti e length on othei finu >i m iti-ulato-ti 

(4) Wire 1 thai have theii outei covering finished ><■> show a 
white or gray color but has-; colored tracer threads in 
the braid identifying the source of manufac hire shall be 
< on'sidered i tv eting the ,'imi ions <u rlu 1 , se< ucn. 

(5) The grounded conductor of a mineral-insulated, metal- 
sheathed cable shall be identified at the time of instal- 
lation by distinctive marking at its terminations. 

(6) A single-conductor, sunlight-resistant, outdoor-rated 
cable used as a grounded conductor in photovoltaic 
power systems, as permitted by 690.31, shall be iden- 
tified at the time of installation by distinctive white 
marking at all terminations. 

(7) Fixture wire shall comply with the requirements for 
grounded conductor identification as specified in 402.8. 

(8) For aerial cable, the identification shall be as above, or 
by means of a ridge located on the exterior of the cable 
so as to identify it. 

(B) Sizes 4 AWG or Larger. An insulated grounded con- 
ductor 4 AWG or larger shall be identified by one of the 
following means: 

(1) A continuous white outer finish. 

(2) A continuous gray outer finish 

(3) Three continuous white stripes along its entire length 
on other than green insulation. 

(4) At the time of installation, by a distinctive white or gray 
marking at its terminations. This marking shall encircle 
the conductor or insulation. 

(C) Flexible Cords. An insulated conductor that is intended 
for use as a grounded conductor, where contained within a 
flexible cord, shall be identified by a white or gray outer finish 
or by methods permitted by 400.22. 

(D) Grounded Conductors of Different Systems. Where 
grounded conductors of different systems are installed in 
the same raceway, cable, box, auxiliary gutter, or other type 
of enclosure, each grounded conductor shall be identified 



70-46 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 200 — USE AND IDENTIFICATION OF GROUNDED CONDUCTORS 



200.10 



by system. Identification that distinguishes each system 
grounded conductor shall be permitted by one of the fol- 
lowing means: 

(1) One system grounded conductor shall have an outer 
covering conforming to 200.6(A) or (B). 

(2) The grounded conductor(s) of other systems shall have 
a different outer covering conforming to 200.6(A) or 
200.6(B) or by an outer covering of white or gray with 
a readily distinguishable colored stripe other than green 
running along the insulation. 

(3) Other and different means of identification as allowed 
by 200.6(A) or (B) that will distinguish each system 
grounded conductor. 

The means of identification shall be documented in a 
manner that is readily available or shall be permanently 
posted where the conductors of different systems originate. 

(E) Grounded Conductors of Multiconductor Cables. 

The insulated grounded conductors in a multiconductor 
cable shall be identified by a continuous white or gray outer 
finish or by three continuous white stripes on other than 
green insulation along its entire length. Multiconductor flat 
cable 4 AWG or larger shall be permitted to employ an 
external ridge on the grounded conductor. 

Exception No. 1: Where the conditions of maintenance 
and supervision ensure that only qualified persons service 
the installation, grounded conductors In multiconductor 
cables shall be permitted to be permanently identified at 
their terminations at the time of installation by a distinctive 
white marking or other equally effective means. 
Exception No. 2: The grounded conductor of a multicon- 
ductor varnished-cloth-insulated cable shall be permitted 
to be identified at its terminations at the time of installation 
by a distinctive white marking or other equally effective 
means. 

Informational Note: The color gray may have been used in 
the past as an ungrounded conductor. Care should be taken 
when working on existing systems. 

200.7 Use of Insulation of a White or Gray Color or 
with Three Continuous White Stripes. 

(A) General. The following shall be used only for the 
grounded circuit conductor, unless otherwise permitted in 
200.7(B) and (C): 

(1) A conductor with continuous white or gray covering 

(2) A conductor with three continuous white stripes on 
other than green insulation 

(3) A marking of white or gray color at the termination 

(B) Circuits of Less Than 50 Volts. A conductor with 
white or gray color insulation or three continuous white stripes 
or having a marking of white or gray at the termination for 



circuits of less than 50 volts shall be required to be grounded 
only as required by 250.20(A). 

(C) Circuits of 50 Volts or More. The use of insulation 
that is white or gray or that has three continuous white 
stripes for other than a grounded conductor for circuits of 
50 volts or more shall be permitted only as in (1) and (2). 

(1) If part of a cable assembly that has the insulation per- 
manently reidentified to indicate its use as an un- 
grounded conductor by marking tape, painting, or other 
effective means at its termination and at each location 
where the conductor is visible and accessible. Identifi- 
cation shall encircle the insulation and shall be a color 
other than white, gray, or green. If used for single-pole. 
3-way or 4-way switch loops i'i'" reidentified conduc- 
tor with white or gray insulation or three continuous 
white stripes shall be used only for the supply to the 
switch, but not as a return conductor from the switch to 
the outlet. 

(2) A flexible cord, having one conductor identified by a 
white or gray outer finish or three continuous white 
stripes or by any other means permitted by 400.22, that 
is used for connecting an appliance or equipment per- 
mitted by 400.7. This shall apply to flexible cords con- 
nected to outlets whether or not the outlet is supplied 
by a circuit that has a grounded conductor. 

Informational Note: The color gray may have been used in 
the past as an ungrounded conductor. Care should be taken 
when working on existing systems. 

200.9 Means of Identification of Terminals. The identifi- 
cation of terminals to which a grounded conductor is to be 
connected shall be substantially white in color. The identi- 
fication of other terminals shall be of a readily distinguish- 
able different color. 

Exception: Where the conditions of maintenance and super- 
vision ensure that only qualified persons service the installa- 
tions, terminals for grounded conductors shall be permitted to 
be permanently identified at the time of installation by a dis- 
tinctive white marking or other equally effective means. 

200.10 Identification of Terminals. 

(A) Device Terminals. All devices, excluding panelboards, 
provided with terminals for the attachment of conductors and 
intended for connection to more than one side of the circuit 
shall have terminals properly marked for identification, unless 
the electrical connection of the terminal intended to be con- 
nected to the grounded conductor is clearly evident. 

Exception: Terminal identification shall not be required for 
devices that have a normal current rating of over 30 amperes, 
other than polarized attachment plugs and polarized recep- 
tacles for attachment plugs as required in 200.10(B). 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-47 



200.11 



ARTICLE 210 — BRANCH CIRCUITS 



(B) Receptacles, Plugs, and Connectors. Receptacles, 
polarized attachment plugs, and cord connectors for plugs 
and polarized plugs shall have the terminal intended for 
connection to the grounded conductor identified as follows: 

(1) Identification shall be by a metal or metal coating that 
is substantially white in color or by the word white or 
the letter W located adjacent to the identified terminal. 

(2) If the terminal is not visible, the conductor entrance 
hole for the connection shall be colored white or 
marked with the word white or the letter W. 

Informational Note: See 250.126 for identification of wir- 
ing device equipment grounding conductor terminals. 

(C) Screw Shells. For devices with screw shells, the ter- 
minal for the grounded conductor shall be the one con- 
nected to the screw shell. 

(D) Screw Shell Devices with Leads. For screw shell de- 
vices with attached leads, the conductor attached to the 
screw shell shall have a white or gray finish. The outer 
finish of the other conductor shall be of a solid color that 
will not be confused with the white or gray finish used to 
identify the grounded conductor. 

Informational Note: The color gray may have been used in 
the past as an ungrounded conductor. Care should be taken 
when working on existing systems. 

(E) Appliances. Appliances that have a single-pole switch 
or a single-pole overcurrent device in the line or any line- 
connected screw shell lampholders, and that are to be con- 
nected by (1) a permanent wiring method or (2) field- 
installed attachment plugs and cords with three or more 
wires (including the equipment grounding conductor), shall 
have means to identify the terminal for the grounded circuit 
conductor (if any). 

200.11 Polarity of Connections. No grounded conductor 
shall be attached to any terminal or lead so as to reverse the 
designated polarity. 



210.2 Other Articles for Specific-Purpose Branch Cir- 
cuits. Branch circuits shall comply with this article and also 
with the applicable provisions of other articles of this Code. 
The provisions for branch circuits supplying equipment 
listed in Table 210.2 amend or supplement the provisions in 
this article and shall apply to branch circuits referred to 
therein. 

210.3 Rating. Branch circuits recognized by this article 
shall be rated in accordance with the maximum permitted 
ampere rating or setting of the overcurrent device. The rat- 
ing for other than individual branch circuits shall be 1 5, 20, 
30, 40, and 50 amperes. Where conductors of higher am- 
pacity are used for any reason, the ampere rating or setting 
of the specified overcurrent device shall determine the cir- 
cuit rating. 

Exception: Multioutlet branch circuits greater than 50 
amperes shall be permitted to supply nonlighting outlet 
loads on industrial premises where conditions of mainte- 
nance and supervision ensure that only qualified persons 
service the equipment. 

210.4 Multiwire Branch Circuits. 

(A) General. Branch circuits recognized by this article shall 
be permitted as multiwire circuits. A multiwire circuit shall be 
permitted to be considered as multiple circuits. All conductors 
of a multiwire branch circuit shall originate from the same 
panelboard or similar distribution equipment. 

Informational Note: A 3-phase, 4-wire, wye-connected power 
system used to supply power to nonlinear loads may necessi- 
tate that the power system design allow for the possibility of 
high harmonic currents on the neutral conductor. 

(B) Disconnecting Means. Each multiwire branch circuit 
shall be provided with a means that will simultaneously 
disconnect all ungrounded conductors at the point where 
the branch circuit originates. 

Informational Note: See 240.15(B) for information on the 
use of single-pole circuit breakers as the disconnecting 
means. 



ARTICLE 210 
Branch Circuits 

I. General Provisions 

210.1 Scope. This article covers branch circuits except for 
branch circuits that supply only motor loads, which are 
covered in Article 430. Provisions of this article and Article 
430 apply to branch circuits with combination loads. 



(C) Line-to-Neutral Loads. Multiwire branch circuits 
shall supply only line- to-neutral loads. 

Exception No. 1: A multiwire branch circuit that supplies 
only one utilization equipment. 

Exception No. 2: Where all ungrounded conductors of the 
multiwire branch circuit are opened simultaneously by the 
branch-circuit overcurrent device. 

Informational Note: See 300.13(B) for continuity of 
grounded conductor on multiwire circuits. 



70-48 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.6 



Table 210.2 Specific-Purpose Branch Circuits 



Equipment 


Article 


Section 


Air-conditioning and 




440.6,440.31, 


refrigerating equipment 




440.32 


Audio signal processing, 




640.8 


amplification, and 






reproduction equipment 






Busways 




368.17 


Circuits and equipment 


720 




operating at less than 50 






volts 






Central heating equipment 




422.12 


other than fixed electric 






space-heating equipment 






Class 1, Class 2, and Class 3 


725 




remote-control, signaling, 






and power-limited circuits 






Cranes and hoists 




610.42 


Electric signs and outline 




600.6 


lighting 






Electric welders 


630 




Electrified truck parking 


626 




space 






Elevators, dumbwaiters, 




620.61 


escalators, moving walks. 






wheelchair lifts, and 






stairway chair lifts 






Fire alarm systems 


760 




Fixed electric heating 




427.4 


equipment for pipelines 






and vessels 






Fixed electric space-heating 




424.3 


equipment 






Fixed outdoor electrical 




426.4 


deicing and snow-melting 






equipment 






Information technology 




645.5 


equipment 






Infrared lamp industrial 




422.48, 424.3 


heating equipment 






Induction and dielectric 


665 




heating equipment 






Marinas and boatyards 




555.19 


Mobile homes, manufactured 


550 




homes, and mobile home 






parks 






Motion picture and television 


530 




studios and similar 






locations 






Motors, motor circuits, and 


430 




controllers 






Pipe organs 




650.7 


Recreational vehicles and 


551 




recreational vehicle parks 






Switchboards and 




408.52 


panelboards 






Theaters, audience areas of 




520.41, 520.52, 


motion picture and 




520.62 


television studios, and 






similar locations 






X-ray equipment 




660.2,517.73 



(D) Grouping. The ungrounded and grounded circuit con- 
ductors of each multiwire branch circuit shall be grouped 
by cable ties or similar means in at least one location within 
the panel hoard or other point of origination. 

Exception: The requirement for grouping shall not apply if 
the circuit enters from a cable or raceway unique to the 
circuit that makes the grouping obvious. 

210.5 Identification for Branch Circuits. 

(A) Grounded Conductor. The grounded conductor of a 
branch circuit shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductor. The equipment 
grounding conductor shall be identified in accordance with 
250.119. 

(C) Id'..- tiiication of Ungrounded Conductors. Un- 

grou ide 3 e<4i<!i)'jf'i- sh: II w id' ni ii ■>' i«i » < ordam c t ith 
2K).5(C)(li. C). and (3). 

(1) Application. Where trie premises wiring system ha-; 
branch circuits supplied from more than one n<«nrnal volt- 
age system, each ungrounded conductor of a branch circuit 
shall tv identified tw phase or line and system at all termi- 
nation, connection, and splice points. 

(2) Means of Identification. The means of identification 
shall be. permitted to be by separate color coding, marking 
tape, tagging, or other approved means. 

(3) Posting of Identification Means. The method ulili/ed 
for conductors originating within each branch- circuit pan- 
elboard or similar branch-circuit distribution equipment 
shall I : documented in a manner that is readily available or 
shall be permanenik posted at each branch-circuit panel- 
board or similar branch-circuit distribution equipment. 

210.6 Branch-Circuit Voltage Limitations. The nominal 
voltage of branch circuits shall not exceed the values per- 
mitted by 210.6(A) through (E). 

(A) Occupancy Limitation. In dwelling units and guest 
rooms or guest suites of hotels, motels, and similar occupan- 
cies, the voltage shall not exceed 120 volts, nominal, between 
conductors that supply the terminals of the following: 

(1) Luminaires 

(2) Cord-and-plug-connected loads 1440 volt-amperes, 
nominal, or less or less than [ A hp 

(B) 120 Volts Between Conductors. Circuits not exceed- 
ing 120 volts, nominal, between conductors shall be permit- 
ted to supply the following: 

(1) The terminals of landholders applied within their volt- 
age ratings 

(2) Auxiliary equipment of electric-discharge lamps 

(3) Cord-and-plug-connected or permanently connected utili- 
zation equipment 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-49 



210.7 



ARTICLE 2)0 — BRANCH CIRCUITS 



(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply the following: 

(1) Listed electric-discharge or listed light-emitting diode- 
type luminaires 

(2) Listed incandescent luminaires, where supplied at 
120 volts or less from the output of a stepdown au- 
totransformer that is an integral component of the 
luminaire and the outer shell terminal is electrically 
connected to a grounded conductor of the branch 
circuit 

(3) Luminaires equipped with mogul-base screw shell 1am- 
pholders 

(4) Lampholders, other than the screw shell type, applied 
within their voltage ratings 

(5) Auxiliary equipment of electric-discharge lamps 

(6) Cord-and-plug-connected or permanently connected 
utilization equipment 

(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the following: 

(1) The auxiliary equipment of electric-discharge lamps 
mounted in permanently installed luminaires where 
the luminaires are mounted in accordance with one 
of the following: 

a. Not less than a height of 6.7 m (22 ft) on poles or 
similar structures for the illumination of outdoor ar- 
eas such as highways, roads, bridges, athletic fields, 
or parking lots 

b. Not less than a height of 5.5 m (18 ft) on other 
structures such as tunnels 

(2) Cord-and-plug-connected or permanently connected 
utilization equipment other than luminaires 

(3) Luminaires powered from direct-current systems where 
the luminaire contains a listed, dc-rated ballast that pro- 
vides isolation between the dc power source and the 
lamp circuit and protection from electric shock when 
changing lamps. 

Informational Note: See 410.138 for auxiliary equipment 
limitations. 

Exception No. 1 to (B), (C), and (D): For lampholders of 
infrared industrial heating appliances as provided in 
422.14. 

Exception No. 2 to (B), (C), and (D): For railway proper- 
ties as described in 110.19. 

(E) Over 600 Volts Between Conductors. Circuits ex- 
ceeding 600 volts, nominal, between conductors shall be 
permitted to supply utilization equipment in installations 
where conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 



210.7 Multiple Branch Circuits. Where two or more 
branch circuits supply devices or equipment on the same 
yoke, a means to simultaneously disconnect the un- 
grounded conductors supplying those devices shall be pro- 
vided at ihe point a.i which the branch circuits originate. 

210.8 Ground-Fault Circuit-Interrupter Protection for 

Personnel. ©rSWd-fault circuit-interruption for personnel 
shall be provided as i'„"|i>"- j d u 210. !(A) diR-uph (C) The 
ground-faull cii ait-mierrupler shall be installed in a 
readily accessible location. 

Informational Note: See 215.9 for ground-fault circuit- 
interrupter protection for personnel on feeders. 

(A) Dwelling Units. All 125-volt, single-phase, 15- and 20- 
ampere receptacles installed in the locations specified in 
210.8(A)(1) through (8) shall have ground-fault circuit- 
interrupter protection for personnel. 

(1) Bathrooms 

(2) Garages, and also accessory buildings that have a floor 
located at or below grade level not intended as habit- 
able rooms and limited to storage areas, work areas, 
and areas of similar use 

(3) Outdoors 

Exception to (3): Receptacles that are not readily acces- 
sible and are supplied by a branch circuit dedicated to 
electric snow-melting deh hip, oi pipeline and vessel heat- 
ing equipment shall be permitted to be installed in accor- 
dance with 426.28 or 427.22, as applicable. 

(4) Crawl spaces — at or below grade level 

(5) Unfinished basements — for purposes of this section, 
unfinished basements are defined as portions or areas of 
the basement not intended as habitable rooms and lim- 
ited to storage areas, work areas, and the like 

Exception to (5): A receptacle supplying only a perma- 
nently installed fire alarm or burglar alarm system shall 
not be required to have ground-fault circuit-interrupter 
protection. 

Informational Note: See 760.41 (B) and 760. 121(B) for power 
supply requirements for fire alarm systems. 

Receptacles installed under the exception to 
210.8(A)(5) shall not be considered as meeting the 
requirements of 210.52(G). 

(6) Kitchens — where the receptacles are installed to serve 
the countertop surfaces 

(7) Sinks — - located in areas other than kitchens where 
receptacles are installed within 1.8 m (6 ft) of the out- 
side edge of the sink 

(8) Boathouses 



70-50 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.11 



(B) Other Than Dwelling Units. All 125 volt, single- 
phase, 15- and 20-ampere receptacles installed in the loca- 
tions specified in 210.8(B)(1) through (8) shall have 
ground-fault circuit-interrupter protection for personnel. 

(1) Bathrooms 

(2) Kitchens 

(3) Rooftops 

(4) Outdoors 

Exception No. 1 to (3) and (4): Receptacles that are not 
readily accessible and are supplied by a branch circuit 
dedicated to electric snow-melting, deicing, or pipeline and 
vessel heating equipment shall be permitted to be installed 
in accordance with 426.28 or 427.22, as applicable. 

Exception No. 2 to (4): In industrial establishments only, 
where the conditions of maintenance and supervision en- 
sure that only qualified personnel are involved, an assured 
equipment grounding conductor program as specified in 
590.6(B)(2) shall be permitted for only those receptacle 
outlets used to supply equipment that would create a 
greater hazard if power is interrupted or having a design 
that is not compatible with GFCI protection. 

(5) Sinks — where receptacles are installed within 1.8 m 
(6 ft) of the outside edge of the sink. 

Exception No. 1 to (5): In industrial laboratories, recep- 
tacles used to supply equipment where removal of power 
would introduce a greater hazard shall be permitted to be 
installed without GFCI protection. 

Exception No. 2 to (5): For re eptot /< v located in patient 
bed locations of general care or critical care areas of 
health care facilities other than those coveted under 
210.8(B)! J), GFCI protection shall not be required. 

(M Indoor wet locations 

(7) Locker rooms with associate S showering facilities 

(8) Garages, service bays, and similar areas where electri- 
cal diagnostic equipment, electrical lid ad tools, or por- 
table lighting equipment are to be used 

(C) Boat Hoists. GFCI protection shall be provided for 
outlets not exceeding 240 volts that supply boat hoists in- 
stalled in dwelling unit locations. 

210.9 Circuits Derived from Autotransformers. Branch 
circuits shall not be derived from autotransformers unless 
the circuit supplied has a grounded conductor that is elec- 
trically connected to a grounded conductor of the system 
supplying the autotransformer. 

Exception No. 1: An autotransformer shall be permitted 
without the connection to a grounded conductor where 
transforming from a nominal 208 volts to a nominal 240- 
volt supply or similarly from 240 volts to 208 volts. 



Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only 
qualified persons service the installation, autotransformers 
shall be permitted to supply nominal 600-volt loads from 
nominal 480-volt systems, and 480-volt loads from nominal 
600-volt systems, without the connection to a similar 
grounded conductor. 

210.10 Ungrounded Conductors Tapped from Grounded 

Systems. Two-wire dc circuits and ac circuits of two or 
more ungrounded conductors shall be permitted to be 
tapped from the ungrounded conductors of circuits that 
have a grounded neutral conductor. Switching devices in 
each tapped circuit shall have a pole in each ungrounded 
conductor. All poles of multipole switching devices shall 
manually switch together where such switching devices 
also serve as a disconnecting means as required by the 
following: 

(1) 410.93 for double-pole switched lampholders 

(2) 410.104(B) for electric-discharge lamp auxiliary equip- 
ment switching devices 

(3) 422.31(B) for an appliance 

(4) 424.20 for a fixed electric space-heating unit 

(5) 426.51 for electric deicing and snow-melting equipment 

(6) 430.85 for a motor controller 

(7) 430.103 for a motor 

210.11 Branch Circuits Required. Branch circuits for 
lighting and for appliances, including motor-operated appli- 
ances, shall be provided to supply the loads calculated in 
accordance with 220.10. In addition, branch circuits shall 
be provided for specific loads not covered by 220.10 where 
required elsewhere in this Code and for dwelling unit loads 
as specified in 210.11(C). 

(A) Number of Branch Circuits. The minimum number 
of branch circuits shall be determined from the total calcu- 
lated load and the size or rating of the circuits used. In all 
installations, the number of circuits shall be sufficient to 
supply the load served. In no case shall the load on any 
circuit exceed the maximum specified by 220.18. 

(B) Load Evenly Proportioned Among Branch Circuits. 

Where the load is calculated on the basis of volt-amperes 
per square meter or per square foot, the wiring system up to 
and including the branch-circuit panelboard(s) shall be pro- 
vided to serve not less than the calculated load. This load 
shall be evenly proportioned among multioutlet branch cir- 
cuits within the panelboard(s). Branch-circuit overcurrent 
devices and circuits shall be required to be installed only to 
serve the connected load. 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-51 



210.12 



ARTICLE 210 — BRANCH CIRCUITS 



(C) Dwelling Units. 

(1) Small-Appliance Branch Circuits. In addition to the 
number of branch circuits required by other parts of this 
section, two or more 20-ampere small-appliance branch cir- 
cuits shall be provided for all receptacle outlets specified by 
210.52(B). 

(2) Laundry Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one additional 20-ampere branch circuit shall be pro- 
vided to supply the laundry receptacle outlet(s) required by 
210.52(F). This circuit shall have no other outlets. 

(3) Bathroom Branch Circuits. In addition to the number 
of branch circuits required by other parts of this section, at 
least one 20-ampere branch circuit shall be provided to 
supply bathroom receptacle outlet(s). Such circuits shall 
have no other outlets. 

Exception: Where the 20-ampere circuit supplies a single 
bathroom, outlets for other equipment within the same 
bathroom shall be permitted to be supplied in accordance 
with 210.23(A)(1) and (A)(2). 

Informational Note: See Examples Dl(a), Dl(b), D2(b), 
and D4(a) in Informative Annex D. 

210.12 Arc-Fault Circuit-Interrupter Protection. 

(A) Dwelling Units. All 120-volt, single phase, 15- and 
20-ampere branch circuits supplying outlets installed in 
dwelling unit family rooms, dining rooms, living rooms, 
parlors, libraries, dens, bedrooms, sunrooms, recreation 
rooms, closets, hallways, or similar rooms or areas shall 
be protected by a listed arc -fault circuit interrupter, 
combination-type, installed to provide protection of the 
branch circuit. 

Informational Note No. 1: For information on types of 
arc-fault circuit interrupters, see UL 1699-1999, Standard 
for Arc-Fault Circuit Interrupters. 

Informational Note No. 2: See 11.6.3(5) of NFPA 72- 
2010, National Fire Alarm and Signaling Code, for infor- 
mation related to secondary power supply requirements for 
smoke alarms installed in dwelling units. 

Informational Note No. 3: See 760.41(B) and 760.121(B) 
for power-supply requirements for fire alarm systems. 

Exception No. I: If RMC, IMC. EMT. Type MC. or steel 
armored Type AC cables meeting the requirements of 
250. ITS and metal outlet and junction boxes are installed 
for the portion of the branch circuit between the branch- 
circuit overcurrenl device and the first outlet, it shall be 
permitted to install an outlet branch-circuit type AFCI at 
the first outlet to provide protection for the remaining por- 
tion of the branch circuit. 

Exception No. 2: Where a listed metal or nonmetallic con- 
duit or tubing is encased in not less than 50 mm (2 In.) of 



concrete for the portion of the branch circuit between the 
branch-circuit overcurrent device an/! the fist outlet, it 
shall be permitted to install an outlet branch-circuit type 
AFCI at the first outlet to provide protection lor the remain- 
itii portion i'i ;,'" branch circuit. 

Exception No. 3: Where an individual branch circuit to a 
fire alarm system installed in accordance with 760.41(B) or 
760.121(B) is installed in RMC, IMC, EMT, or steel- 
sheathed cable, Type AC or Type MC, meeting the require- 
ments of 250.118, with metal outlet and junction boxes, 
AFCI protection shall be permitted, to be omitted. 

(B) Branch Cirss; i ^tensions or Modifications — Dwell- 
ing Units. In any of the areas specified in 210.12(A), where 
oia.n h > in Ml >- (ring i mo mi. d, ,>•;>> u ed ut • saend ;d dr. 
branch circuit shall be protected by one of the following: 

(1) A listed combination-type AFCI located at the origin of 
the branch circuit 

(2) A listed outlet branch-circuit type AFCI located at the 
first receptacle outlet of the existing branch circuit 

210.18 Guest Rooms and Guest Suites. Guest rooms and 
guest suites that are provided with permanent provisions for 
cooking shall have branch circuits installed to meet the 
rules for dwelling units. 

II. Branch-Circuit Ratings 

210.19 Conductors — Minimum Ampacity and Size. 

(A) Branch Circuits Not More Than 600 Volts. 

(1) General. Branch-circuit conductors shall have an am- 
pacity not less than the maximum load to be served. Where 
a branch circuit supplies continuous loads or any combina- 
tion of continuous and noncontinuous loads, the minimum 
branch-circuit conductor size, before the application of any 
adjustment or correction factors, shall have an allowable am- 
pacity not less than the noncontinuous load plus 125 percent 
of the continuous load. 

Exception: If the assembly, including the overcurrent de- 
vices protecting the branch circuit(s), is listed for operation 
at 100 percent of its rating, the allowable ampacity of the 
branch circuit conductors shall be permitted to be not less 
than the sum of the continuous load plus the noncontinuous 
load. 

Informational Note No. 1 : See 3 1 0. 15 for ampacity ratings 
of conductors. 

Informational Note No. 2: See Part II of Article 430 for 
minimum rating of motor branch-circuit conductors. 

Informational Note No. 3: See 310.15(A)(3) for tempera- 
ture limitation of conductors. 



70-52 



NATIONAL ELECTRICAL CODE 201.1 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.20 



Informational Note No. 4: Conductors for branch circuits 
as defined in Article 100, sized to prevent a voltage drop 
exceeding 3 percent at the farthest outlet of power, heating, 
and lighting loads, or combinations of such loads, and 
where the maximum total voltage drop on both feeders and 
branch circuits to the farthest outlet does not exceed 5 per- 
cent, provide reasonable efficiency of operation. See Infor- 
mational Note No. 2 of 215.2(A)(3) for voltage drop on 
feeder conductors. 

(2) Branch Circuits with More than One Receptacle. 

Conductors of branch circuits supplying more than one re- 
ceptacle for cord-and-plug-connected portable loads shall 
have an ampacity of not less than the rating of the branch 
circuit. 

(3) Household Ranges and Cooking Appliances. Branch- 
circuit conductors supplying household ranges, wall- 
mounted ovens, counter-mounted cooking units, and other 
household cooking appliances shall have an ampacity not 
less than the rating of the branch circuit and not less than 
the maximum load to be served. For ranges of 8% kW or 
more rating, the minimum branch-circuit rating shall be 
40 amperes. 

Exception No. 1: Conductors tapped from a 50-ampere 
branch circuit supplying electric ranges, wall-mounted 
electric ovens, and counter-mounted electric cooking units 
shall have an ampacity of not less than 20 amperes and 
shall be sufficient for the load to be served. These tap con- 
ductors include any conductors that are a part of the leads 
supplied with the appliance that are smaller than the 
branch-circuit conductors. The taps shall not be longer 
than necessary for servicing the appliance. 

Exception No. 2: The neutral conductor of a 3-wire 
branch circuit supplying a household electric range, a 
wall-mounted oven, or a counter-mounted cooking unit 
shall be permitted to be smaller than the ungrounded con- 
ductors where the maximum demand of a range of 8 3 A-kW 
or more rating has been calculated according to Column C 
of Table 220.55, but such conductor shall have an ampacity 
of not less than 70 percent of the branch-circuit rating and 
shall not be smaller than 10 AWG. 

(4) Other Loads. Branch-circuit conductors that supply 
loads other than those specified in 210.2 and other than 
cooking appliances as covered in 210.19(A)(3) shall have 
an ampacity sufficient for the loads served and shall not be 
smaller than 14 AWG. 

Exception No. I: Tap conductors shall have an ampacity 
sufficient for the load served. In addition, they shall have an 
ampacity of not less than 15 for circuits rated less than 
40 amperes and not less than 20 for circuits rated at 40 or 
50 amperes and only where these tap conductors supply 
any of the following loads: 



(a) Individual lampholders or luminaires with taps ex- 
tending not longer than 450 mm (18 in.) beyond any por- 
tion of the lampholder or luminaire. 

(b) A luminaire having tap conductors as provided in 
410.117. 

(c) Individual outlets, other than receptacle outlets, 
with taps not over 450 mm (18 in.) long. 

(d) Infrared lamp industrial heating appliances. 

(e) Nonhealing leads of deicing and snow-melting 
cables and mats. 

Exception No. 2: Fixture wires and flexible cords shall be 
permitted to be smaller than 14 AWG as permitted by 
240.5. 

(B) Branch Circuits Over 600 Volts. The ampacity of 
conductors shall be in accordance with 310.15 and 310.60, 
as applicable. Branch-circuit conductors over 600 volts 
shall be sized in accordance with 210.19(B)(1) or (B)(2). 

(1) General. The ampacity of branch-circuit conductors shall 
not be less than 125 percent of the designed potential load of 
utilization equipment that will be operated simultaneously. 

(2) Supervised Installations. For supervised installations, 
branch-circuit conductor sizing shall be permitted to be de- 
termined by qualified persons under engineering supervi- 
sion. Supervised installations are defined as those portions 
of a facility where both of the following conditions are met: 

(1) Conditions of design and installation are provided un- 
der engineering supervision. 

(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

210.20 Overcurrent Protection. Branch-circuit conduc- 
tors and equipment shall be protected by overcurrent pro- 
tective devices that have a rating or setting that complies 
with 210.20(A) through (D). 

(A) Continuous and Noncontinuous Loads. Where a 
branch circuit supplies continuous loads or any combi- 
nation of continuous and noncontinuous loads, the rating 
of the overcurrent device shall not be less than the non- 
continuous load plus 125 percent of the continuous load. 

Exception: Where the assembly, including the overcurrent 
devices protecting the branch circuit(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

(B) Conductor Protection. Conductors shall be protected 
in accordance with 240.4. Flexible cords and fixture wires 
shall be protected in accordance with 240.5. 

(C) Equipment. The rating or setting of the overcurrent 
protective device shall not exceed that specified in the ap- 
plicable articles referenced in Table 240.3 for equipment. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-53 



210.21 



ARTICLE 210 — BRANCH CIRCUITS 



(D) Outlet Devices. The rating or setting shall not exceed 
that specified in 210.21 for outlet devices. 

210.21 Outlet Devices. Outlet devices shall have an am- 
pere rating that is not less than the load to be served and 
shall comply with 210.21(A) and (B). 

(A) Lampholders. Where connected to a branch circuit 
having a rating in excess of 20 amperes, lampholders shall 
be of the heavy-duty type. A heavy-duty lampholder shall 
have a rating of not less than 660 watts if of the admedium 
type, or not less than 750 watts if of any other type. 

(B) Receptacles. 

(1) Single Receptacle on an Individual Branch Circuit. 

A single receptacle installed on an individual branch circuit 
shall have an ampere rating not less than that of the branch 
circuit. 

Exception No. 1: A receptacle installed in accordance 
with 430.81(B). 

Exception No. 2: A receptacle installed exclusively for the 
use of a cord-and-plug-connected arc welder shall be permit- 
ted to have an ampere rating not less than the minimum 
branch-circuit conductor ampacity determined by 630.11(A) 
for arc welders. 

Informational Note: See the definition of receptacle in 
Article 100. 

(2) Total Cord-and-Plug-Connected Load. Where con- 
nected to a branch circuit supplying two or more receptacles 
or outlets, a receptacle shall not supply a total cord-and-plug- 
connected load in excess of the maximum specified in Table 

210.21(B)(2). 



Table 210.21(B)(2) Maximum Cord-and-Plug-Connected 
Load to Receptacle 



Circuit Rating Receptacle Rating Maximum Load 
(Amperes) (Amperes) (Amperes) 



15 or 20 
20 
30 



15 
20 
30 



12 
16 

24 



(3) Receptacle Ratings. Where connected to a branch cir- 
cuit supplying two or more receptacles or outlets, recep- 
tacle ratings shall conform to the values listed in Table 
210.21(B)(3), or, where rated higher than 50 amperes, the 
receptacle rating shall not be less than the branch-circuit 
rating. 

Exception No. 1: Receptacles for one or more cord-and- 
plug-connected arc welders shall be permitted to have am- 
pere ratings not less than the minimum branch-circuit con- 



ductor ampacity permitted by 630.11(A) or (B), as 
applicable for arc welders. 

Exception No. 2: The ampere rating of a receptacle in- 
stalled for electric discharge lighting shall be permitted to 
be based on 410.62(C). 



Table 210.21(B)(3) Receptacle Ratings for Various Size 
Circuits 



Circuit Rating 


Receptacle Rating 


(Amperes) 


(Amperes) 


15 


Not over 15 


20 


15 or 20 


30 


30 


40 


40 or 50 


50 


50 



(4) Range Receptacle Rating. The ampere rating of a 
range receptacle shall be permitted to be based on a single 
range demand load as specified in Table 220.55. 

210.23 Permissible Loads. In no case shall the load ex- 
ceed the branch-circuit ampere rating. An individual branch 
circuit shall be permitted to supply any load for which it is 
rated. A branch circuit supplying two or more outlets or 
receptacles shall supply only the loads specified according 
to its size as specified in 210.23(A) through (D) and as 
summarized in 210.24 and Table 210.24. 

(A) 15- and 20-Ampere Branch Circuits. A 15- or 20- 

ampere branch circuit shall be permitted to supply lighting 
units or other utilization equipment, or a combination of 
both, and shall comply with 210.23(A)(1) and (A)(2). 

Exception: The small-appliance branch circuits, laundry 
branch circuits, and bathroom branch circuits required in a 
dwelling unit(s) by 210.11(C)(1), (C)(2), and (C)(3) shall 
supply only the receptacle outlets specified in that section. 

(1) Cord-and-Plug-Connected Equipment Not Fastened 

in Place. The rating of any one cord-and-plug-connected 
utilization equipment not fastened in place shall not exceed 
80 percent of the branch-circuit ampere rating. 

(2) Utilization Equipment Fastened in Place. The total 
rating of utilization equipment fastened in place, other than 
luminaires, shall not exceed 50 percent of the branch- 
circuit ampere rating where lighting units, cord-and-plug- 
connected utilization equipment not fastened in place, or 
both, are also supplied. 

(B) 30- Ampere Branch Circuits. A 30-ampere branch cir- 
cuit shall be permitted to supply fixed lighting units with 
heavy-duty lampholders in other than a dwelling unit(s) or 
utilization equipment in any occupancy. A rating of any one 



70-54 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.52 



cord-and-plug-connected utilization equipment shall not 
exceed 80 percent of the branch-circuit ampere rating. 

(C) 40- and 50-Ampere Branch Circuits. A 40- or 50 

ampere branch circuit shall be permitted to supply cook- 
ing appliances that are fastened in place in any occu- 
pancy. In other than dwelling units, such circuits shall be 
permitted to supply fixed lighting units with heavy-duty lam- 
pholders, infrared heating units, or other utilization equipment. 

(D) Branch Circuits Larger Than 50 Amperes. Branch 
circuits larger than 50 amperes shall supply only nonlight- 
ing outlet loads. 

210.24 Branch-Circuit Requirements — Summary. The 

requirements for circuits that have two or more outlets or 
receptacles, other than the receptacle circuits of 210.11(C)(1)* 
(C)(2), and (C)(3), are summarized in Table 210.24. This table 
provides only a summary of minimum requirements. See 
210.19, 210.20, and 210.21 for the specific requirements ap- 
plying to branch circuits. 

210.25 Branch Circuits in Buildings with More Than 
One Occupancy. 

(A) Dwelling Unit Branch Circuits. Branch circuits in 
each dwelling unit shall supply only loads within that dwelling 
unit or loads associated only with that dwelling unit. 

(B) Common Area Branch Circuits. Branch circuits in- 
stalled for the purpose of lighting, central alarm, signal, com- 
munications, or other purposes for public or common areas of 
a two-family dwelling, a multifamily dwelling, or a multi- 
occupancy building shall not be supplied from equipment that 
supplies an individual dwelling unit or tenant space. 

Table 210.24 Summary of Branch-Circuit Requirements 



III. Required Outlets 

210.50 General. Receptacle outlets shall be installed as 
specified in 210.52 through 210.63. 

(A) Cord Pendants. A cord connector that is supplied by a 
permanently connected cord pendant shall be considered a 
receptacle outlet. 

(B) Cord Connections. A receptacle outlet shall be in- 
stalled wherever flexible cords with attachment plugs are 
used. Where flexible cords are permitted to be permanently 
connected, receptacles shall be permitted to be omitted for 
such cords. 

(C) Appliance Receptacle Outlets. Appliance receptacle 
outlets installed in a dwelling unit for specific appliances, 
such as laundry equipment, shall be installed within 1.8 m 
(6 ft) of the intended location of the appliance. 

210.52 Dwelling Unit Receptacle Outlets. This section 
provides requirements for 125-volt, 15- and 20-ampere re- 
ceptacle outlets. The receptacles required by this section 
shall be in addition to any receptacle that is: 

(1) Part of a luminaire or appliance, or 

(2) Controlled by a wall switch in accordance with 
210.70(A)(1), Exception No. 1, or 

(3) Located within cabinets or cupboards, or 

(4) Located more than 1.7 m (5 x h ft) above the floor 
Permanently installed electric baseboard heaters equipped 

with factory-installed receptacle outlets or outlets provided as 
a separate assembly by the manufacturer shall be permitted as 
the required outlet or outlets for the wall space utilized by 



Circuit Rating 


15 A 


20 A 


30 A 


40 A 


50 A 


Conductors (min. size): 
Circuit wires 1 
Taps 

Fixture wires and cords 
— see 240.5 


14 
14 


12 
14 


10 

14 


8 
12 


6 
12 


Overcurrent 
Protection 


15 A 


20 A 


30 A 


40 A 


50 A 


Outlet devices: 
Lampliolders 
permitted 
Receptacle rating 2 


Any type 
15 max. A 


Any type 
15 or 20 A 


Heavy duty 
30 A 


Heavy duty 
40 or 50 A 


Heavy duty 
50 A 


Maximum Load 


15 A 


20 A 


30 A 


40 A 


50 A 


Permissible load 


See 210.23(A) 


See 210.23(A) 


See 210.23(B) 


See 210.23(C) 


See 210.23(C) 



'These gauges are for copper conductors. 

"For receptacle rating of cord-connected electric-discharge luminaires, see 410.62(C). 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-55 



210.52 



ARTICLE 210 — BRANCH CIRCUITS 



such permanently installed heaters. Such receptacle outlets 
shall not be connected to the heater circuits. 

Informational Note: Listed baseboard heaters include in- 
structions that may not permit their installation below re- 
ceptacle outlets. 

(A) General Provisions. In every kitchen, family room, 
dining room, living room, parlor, library, den, sunroom, 
bedroom, recreation room, or similar room or area of 
dwelling units, receptacle outlets shall be installed in accor- 
dance with the general provisions specified in 210.52(A)(1) 
through (A)(3). 

(1) Spacing. Receptacles shall be installed such that no 
point measured horizontally along the floor line of any wall 
space is more than 1.8 m (6 ft) from a receptacle outlet. 

(2) Wall Space. As used in this section, a wall space shall 
include the following: 

(1) Any space 600 mm (2 ft) or more in width (including 
space measured around corners) and unbroken along 
the floor line by doorways and dmilai openings, fire- 
places, and fixed cabinets 

(2) The space occupied by fixed panels in exterior walls, 
excluding sliding panels 

(3) The space afforded by fixed room dividers, such as 
freestanding bar-type counters or railings 

(3) Floor Receptacles. Receptacle outlets in floors shall 
not be counted as part of the required number of receptacle 
outlets unless located within 450 mm (18 in.) of the wall. 

(4) Countertop Receptacles. Receptacles installed for coun- 
tertop surfaces as specified in 210.52(C) shall irf he consid 
ered as the receptacles required by 210.52(A). 

(B) Small Appliances. 

(1) Receptacle Outlets Served. In the kitchen, pantry, 
breakfast room, dining room, or similar area of a dwelling 
unit, the two or more 20-ampere small-appliance branch 
circuits required by 210.11(C)(1) shall serve all wall and 
floor receptacle outlets covered by 210.52(A), all counter- 
top outlets covered by 210.52(C), and receptacle outlets for 
refrigeration equipment. 

Exception No. 1: In addition to the required receptacles 
specified by 210.52, switched receptacles supplied from a 
general-purpose branch circuit as defined in 210.70(A)(1), 
Exception No. 1, shall be permitted. 

Exception No. 2: The receptacle outlet for refrigeration 
equipment shall be permitted to be supplied from an indi- 
vidual branch circuit rated 15 amperes or greater. 

(2) No Other Outlets. The two or more small-appliance 
branch circuits specified in 210.52(B)(1) shall have no 
other outlets. 



Exception No. 1: A receptacle installed solely for the elec- 
trical supply to and support of an electric clock in any of 
the rooms specified in 210.52(B)(1). 

Exception No. 2: Receptacles installed to provide power 
for supplemental equipment and lighting on gas-fired 
ranges, ovens, or counter-mounted cooking units. 

(3) Kitchen Receptacle Requirements. Receptacles in- 
stalled in a kitchen to serve countertop surfaces shall be 
supplied by not fewer than two small-appliance branch cir- 
cuits, either or both of which shall also be permitted to supply 
receptacle outlets in the same kitchen and in other rooms 
specified in 210.52(B)(1). Additional small-appliance branch 
circuits shall be permitted to supply receptacle outlets in the 
kitchen and other rooms specified in 210.52(B)(1). No small- 
appliance branch circuit shall serve more than one kitchen. 

(C) Countertops. In kitchens, pantries, breakfast rooms, 
dining rooms, and similar areas of dwelling units, recep- 
tacle outlets for countertop spaces shall be installed in ac- 
cordance with 210.52(C)(1) through (C)(5). 

• 

(1) Wall Countertop Spaces. A receptacle outlet shall be 
installed at each wall countertop space that is 300 mm 
(12 in.) or wider. Receptacle outlets shall be installed so 
that no point along the wall line is more than 600 mm 
(24 in.) measured horizontally from a receptacle outlet in 
that space. 

Exception: Receptacle outlets shall not be required on a wall 
directly behind a range, counter-mounted cooking unit, or sink 
in the installation described in Figure 210.52(C)(1). 

(2) Island Countertop Spaces. At least one receptacle 
shall be installed at each island countertop space with a 
long dimension of 600 mm (24 in.) or greater and a short 
dimension of 300 mm (12 in.) or greater. 

(3) Peninsular Countertop Spaces. At least one recep- 
tacle outlet shall be installed at each peninsular countertop 
space with a long dimension of 600 mm (24 in.) or greater and 
a short dimension of 300 mm (12 in.) or greater. A peninsular 
countertop is measured from the connecting edge. 

(4) Separate Spaces. Countertop spaces separated by 
rangetops, refrigerators, or sinks shall be considered as 
separate countertop spaces in applying the requirements of 
210.52(C)(1). If a range, counter-mounted cooking unit, or 
sink is installed in an island or peninsular countertop and 
the depth of the countertop behind the range, counter- 
mounted cooking usiij, or sink is less than 300 mm (12 in.), 
the range, counter-mounted cooking unit, or sink shall be 
consideied to divide the countertop space into two separate 
counteitnp spaces, Each separate countertop space shall 
comply with the applicable requirements in 210.52(C). 



70-56 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 210 — BRANCH CIRCUITS 



210.52 



< Outlet within 

600 mm (24 in.) 




Space exempt from wall 
line if X< 300 mm (12 in.) 




_ Outlet within 
600 mm (24 in.) 




t 
X 

I 








f \ 
V J 















Range, counter-mounted cooking unit extending 
from face of counter 



Space exempt from wall line 
if X< 450 mm (18 in.) 



Outlet within 600 mm (24 in.) - 




Range, counter-mounted cooking unit mounted in corner 

Figure 210.52(C)(1) Determination of Area Behind a Range, 
or Counter-Mounted Cooking Unit or Sink. 

(5) Receptacle Outlet Location. Receptacle outlets shall 
be located on or above, but not more than 500 mm (20 in.) 
above, the countertop. Receptacle outlet as smblie? list d 
for the application shall be prpiwied to be installed in 
couniertops. Receptacle outlets rendered not readily acces- 
sible by appliances fastened in place, appliance garages, 
sinks, or rangetops as covered in 210.52(C)(1), Exception, 
or appliances occupying dedicated space shall not be con- 
sidered as these required outlets. 

Informational Note: See 10" & tc« .r^i'Jii- it nt for in- 
stallation of recepuu les n countcrtops. 

Exception to (5): To comply with the conditions specified in 
(1) or (2), receptacle outlets shall be permitted to be 
mounted not more than 300 mm (12 in.) below the counter- 
top. Receptacles mounted below a countertop in accor- 
dance with this exception shall not be located where the 
countertop extends more than 150 mm (6 in.) beyond its 
support base. 



(1) Construction for the physically impaired 

(2) On island and peninsular countertops where the coun- 
tertop is flat across its entire surface (no backsplashes, 
dividers, etc.) and there are no means to mount a re- 
ceptacle within 500 mm. (20 in.) above the countertop, 
such as an overhead cabinet 

(D) Bathrooms. In dwelling units, at least one receptacle 
outlet shall be installed in bathrooms within 900 mm (3 ft) 
of the outside edge of each basin. The receptacle outlet 
shall be located on a wall or partition that is adjacent to the 
basin or basin countertop, located on the countertop, or 
installed on the side or face of the basin cabinet not more 
than 300 mm (12 in.) below the countertop. Receptacle 
outlet assemblies listed for the application shall be permit- 
ted to he installed in the countertop. 

Informational Note: See 406.5(E) for requirements for in- 
stallation oi receptacles in countertops. 

(E) Outdoor Outlets. Outdoor receptacle outlets shall be 
installed in accordance with (E)(1) through (E)(3). [See 
210.8(A)(3).] 

(1) One-Family and Two-Family Dwellings. For a one- 
family dwelling and each unit of a two-family dwelling that 
is at grade level, at least one receptacle outlet accessible 
while standing at grade level and located not more than 
2.0 m (6!/2 ft) above grade shall be installed at the front and 
back of the dwelling. 

(2) Multifamily Dwellings. For each dwelling unit of a 
multifamily dwelling where the dwelling unit is located 
at grade level and provided with individual exterior 
entrance/egress, at least one receptacle outlet accessible 
from grade level and not more than 2.0 m (6 'A ft) above 
grade shall be installed. 

(3) Balconies, Decks, and Porches. Balconies, decks, and 
porches that are accessible from inside the dwelling unit 
shall have at least one receptacle outlet installed within the 
perimeter of the balcony, deck, or porch. The receptacle 
shall not be located more than 2.0 m (6V2 ft) above the 
balcony, deck, or porch surface. 

(F) Laundry Areas. In dwelling units, at least one recep- 
tacle outlet shall be installed for the laundry. 

Exception No. 1: In a dwelling unit that is an apartment 
or living area in a multifamily building where laundry fa- 
cilities are provided, on the premises and are available to 
all building occupants, a laundry receptacle shall not be 
required. 

Exception No. 2: In other than one-family dwellings where 
laundry facilities are not to be installed or permitted, a 
laundry receptacle shall not be required. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-57 



210.60 



ARTICLE 210 — BRANCH CIRCUITS 



(G) Basements, Garages, and Accessory Buildings. For 

a one-family dwelling, the following provisions shall apply: 

(1) At least one receptacle outlet, in addition to those for 
specific equipment, shall be installed in each basement, 
in each attached garage, and in each detached garage or 
accessory building with electric power. 

(2) Where a portion of the basement is finished into one or 
more habitable rooms, each separate unfinished portion 
shall have a receptacle outlet installed in accordance 
with this section. 

(H) Hallways. In dwelling units, hallways of 3.0 m (10 ft) 
or more in length shall have at least one receptacle outlet. 
As used in this subsection, the hallway length shall be 
considered the length along the centerline of the hallway 
without passing through a doorway. 

(I) Foyers. Foyers that are not part of a hallway in accor- 
dance with 210.52(H) and that have an area that is greater 
than 5.6 nr (60 ft 2 ) shall have a receptacle(s) located in 
each wall space 900 mm (3 ft) or more in width and un- 
broken by doorways, floor-to-ceiling windows, and similar 
openings. 

210.60 Guest Rooms, Guest Suites, Dormitories, and 
Similar Occupancies. 

(A) General. Guest rooms or guest suites in hotels, motels, 
sleeping rooms in dormitories, and similar occupancies shall 
have receptacle outlets installed in accordance with 210.52(A) 
and (D). Guest rooms or guest suites provided with permanent 
provisions for cooking shall have receptacle outlets installed in 
accordance with all of the applicable rules in 210.52. 

(B) Receptacle Placement. In applying the provisions of 
210.52(A), the total number of receptacle outlets shall not 
be less than the minimum number that would comply with 
the provisions of that section. These receptacle outlets shall 
be permitted to be located conveniently for permanent fur- 
niture layout. At least two receptacle outlets shall be readily 
accessible. Where receptacles are installed behind the bed, 
the receptacle shall be located to prevent the bed from 
contacting any attachment plug that may be installed or the 
receptacle shall be provided with a suitable guard. 

210.62 Show Windows. At least one receptacle outlet 
shall be installed within 450 mm (18 in.) of the top of a 
show window for each 3.7 linear m (12 linear ft) or major 
fraction thereof of show window area measured horizon- 
tally at its maximum width. 

210.63 Heating, Air-Conditioning, and Refrigeration 
Equipment Outlet. A 125-volt, single-phase, 15- or 20- 
ampere-rated receptacle outlet shall be installed at an acces- 
sible location for the servicing of heating, air-conditioning, 
and refrigeration equipment. The receptacle shall be located 



on the same level and within 7.5 m (25 ft) of the heating, 
air-conditioning, and refrigeration equipment. The receptacle 
outlet shall not be connected to the load side of the equipment 
disconnecting means. 

Exception: A receptacle outlet shall not be required at 
one- and two-family dwellings for the service of evapora- 
tive coolers. 

Informational Note: See 210.8 for ground-fault circuit- 
interrupter requirements. 

210.70 Lighting Outlets Required. Lighting outlets shall 
be installed where specified in 210.70(A), (B), and (C). 

(A) Dwelling Units. In dwelling units, lighting outlets 
shall be installed in accordance with 210.70(A)(1), (A)(2), 
and (A)(3). 

(1) Habitable Rooms. At least one wall switch-controlled 
lighting outlet shall be installed in every habitable room 
and bathroom. 

Exception No. I: In other than kitchens and bathrooms, 
one or more receptacles controlled by a wall switch shall 
be permitted in lieu of lighting outlets. 

Exception No. 2: Lighting outlets shall be permitted to be 
controlled by occupancy sensors that are (1) in addition to 
wall switches or (2) located at a customary wall switch 
location and equipped with a manual override that will 
allow the sensor to function as a wall switch. 

(2) Additional Locations. Additional lighting outlets shall 
be installed in accordance with (A)(2)(a), (A)(2)(b), and 
(A)(2)(c). 

(a) At least one wall switch-controlled lighting outlet 
shall be installed in hallways, stairways, attached garages, 
and detached garages with electric power. 

(b) For dwelling units, attached garages, and detached 
garages with electric power, at least one wall switch- 
controlled lighting outlet shall be installed to provide illu- 
mination on the exterior side of outdoor entrances or exits 
with grade level access. A vehicle door in a garage shall not 
be considered as an outdoor entrance or exit. 

(c) Where one or more lighting outlet(s) are installed 
for interior stairways, there shall be a wall switch at each 
floor level, and landing level that includes an entryway, to 
control the lighting outlet(s) where the stairway between 
floor levels has six risers or more. 

Exception to (A)(2)(a), (A)(2)(b), and (A)(2)(c): In hall- 
ways, in stairways, and at outdoor entrances, remote, cen- 
tral, or automatic control of lighting shall be permitted. 

(3) Storage or Equipment Spaces. For attics, underfloor 
spaces, utility rooms, and basements, at least one lighting 
outlet containing a switch or controlled by a wall switch 
shall be installed where these spaces are used for storage or 



70-58 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 215 — FEEDERS 



215.2 



contain equipment requiring servicing. At least one point of 
control shall be at the usual point of entry to these spaces. 
The lighting outlet shall be provided at or near the equip- 
ment requiring servicing. 

(B) Guest Rooms or Guest Suites. In hotels, motels, or 
similar occupancies, guest rooms or guest suites shall have 
at least one wall switch-controlled lighting outlet installed 
in every habitable room and bathroom. 

Exception No. 1: In other than bathrooms and kitchens 
where provided, one or more receptacles controlled by a 
wall switch shall be permitted in lieu of lighting outlets. 
Exception No. 2: Lighting outlets shall be permitted to be 
controlled by occupancy sensors that are (1) in addition to 
wall switches or (2) located at a customary wall switch 
location and equipped with a manual override that allows 
the sensor to function as a wall switch. 

(C) Other Than Dwelling Units. For attics and underfloor 
spaces containing equipment requiring servicing, such as 
heating, air-conditioning, and refrigeration equipment, at 
least one lighting outlet containing a switch or controlled 
by a wall switch shall be installed in such spaces. At least 
one point of control shall be at the usual point of entry to 
these spaces. The lighting outlet shall be provided at or 
near the equipment requiring servicing. 



ARTICLE 215 
Feeders 



215.1 Scope. This article covers the installation require- 
ments, overcurrent protection requirements, minimum size, 
and ampacity of conductors for feeders supplying branch- 
circuit loads. 

Exception: Feeders for electrolytic cells as covered in 
668.3(C)(1) and (C)(4). 

215.2 Minimum Rating and Size. 

(A) Feeders Not More Than 600 Volts. 

(1) General. Feeder conductors shall have an ampacity not 
less than required to supply the load as calculated in Parts 
III, IV, and V of Article 220. The minimum feeder-circuit 
conductor size, before the application of any adjustment or 
correction factors, shall have an allowable ampacity not 
less than the noncontinuous load plus 125 percent of the 
continuous load. 

Exception No. J: If the assembly, including the overcur- 
rent devices protecting the feeder(s), is listed for operation 
at 100 percent of its rating, the allowable ampacity of the 



feeder conductors shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

Exception No. 2: Grounded conductors that are not con- 
nected to an overcurrent device shall be permitted to be 
sized at 100 percent of the continuous and noncontinuous 
load. 

(2) Grounded Conductor. The size of the feeder circuit 
grounded conductor shall not be smaller than that required 
by 250.122, except that 250.122(F) shall not apply where 
grounded conductors are run in parallel. 

Additional minimum sizes shall be as specified in 
215.2(A)(2) and (A)(3) under the conditions stipulated. 

(3) Ampacity Relative to Service Conductors. The feeder 
conductor ampacity shall not be less than that of the service 
conductors where the feeder conductors carry the total load 
supplied by service conductors with an ampacity of 55 am- 
peres or less. 

(4) Individual Dwelling Unit or Mobile Home Conduc- 
tors. Feeder conductors for individual dwelling units or 
mobile homes need not be larger than service conductors. 
Paragraph 310.15(B)(6) shall be permitted to be used for 
conductor size. 

Informational Note No. 1: See Examples Dl through Dll in 
Informative Annex D. 

Informational Note No. 2: Conductors for feeders as de- 
fined in Article 1 00, sized to prevent a voltage drop exceed- 
ing 3 percent at the farthest outlet of power, heating, and 
lighting loads, or combinations of such loads, and where 
the maximum total voltage drop on both feeders and branch 
circuits to the farthest outlet does not exceed 5 percent, will 
provide reasonable efficiency of operation. 

Informational Note No. 3: See 210.19(A), Informational 
Note No. 4, for voltage drop for branch circuits. 

(B) Feeders over 600 Volts. The ampacity of conductors 
shall be in accordance with 310.15 and 310.60 as applicable. 
Where installed, the size of the feeder-circuit grounded con- 
ductor shall not be smaller than that required by 250.122, 
except that 250.122(F) shall not apply where grounded con- 
ductors are run in parallel. Feeder conductors over 600 volts 
shall be sized in accordance with 215.2(B)(1), (B)(2), or 
(B)(3). 

(1) Feeders Supplying Transformers. The ampacity of 
feeder conductors shall not be less than the sum of the 
nameplate ratings of the transformers supplied when only 
transformers are supplied. 

(2) Feeders Supplying Transformers and Utilization 
Equipment. The ampacity of feeders supplying a combina- 
tion of transformers and utilization equipment shall not be 
less than the sum of the nameplate ratings of the transform- 
ers and 125 percent of the designed potential load of the 
utilization equipment that will be operated simultaneously. 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-59 



215.3 



ARTICLE 215 — FEEDERS 



(3) Supervised Installations. For supervised installations, 
feeder conductor sizing shall be permitted to be determined 
by qualified persons under engineering supervision. Super- 
vised installations are denned as those portions of a facility 
where all of the following conditions are met: 

(1) Conditions of design and installation are provided un- 
der engineering supervision. 

(2) Qualified persons with documented training and expe- 
rience in over 600-volt systems provide maintenance, 
monitoring, and servicing of the system. 

215.3 Overcurrent Protection. Feeders shall be protected 
against overcurrent in accordance with the provisions of 
Part I of Article 240. Where a feeder supplies continuous 
loads or any combination of continuous and noncontinuous 
loads, the rating of the overcurrent device shall not be less 
than the noncontinuous load plus 125 percent of the con- 
tinuous load. 

Exception No. 1: Where the assembly, including the over- 
current devices protecting the feeder(s), is listed for opera- 
tion at 100 percent of its rating, the ampere rating of the 
overcurrent device shall be permitted to be not less than the 
sum of the continuous load plus the noncontinuous load. 

Exception No. 2: Overcurrent protection for feeders over 
600 volts, nominal, shall comply with Part IX of Article 240. 

215.4 Feeders with Common Neutral Conductor. 

(A) Feeders with Common Neutral. Up to three sets of 
3-wire feeders or two sets of 4-wire or 5-wire feeders shall 
be permitted to utilize a common neutral. 

(B) In Metal Raceway or Enclosure. Where installed in a 
metal raceway or other metal enclosure, all conductors of 
all feeders using a common neutral conductor shall be en- 
closed within the same raceway or other enclosure as re- 
quired in 300.20. 

215.5 Diagrams of Feeders. If required by the authority 
having jurisdiction, a diagram showing feeder details shall 
be provided prior to the installation of the feeders. Such a 
diagram shall show the area in square feet of the building 
or other structure supplied by each feeder, the total calcu- 
lated load before applying demand factors, the demand fac- 
tors used, the calculated load after applying demand fac- 
tors, and the size and type of conductors to be used. 

215.6 Feeder Equipment Grounding Conductor. Where 
a feeder supplies branch circuits in which equipment 
grounding conductors are required, the feeder shall include 
or provide an equipment grounding conductor in accor- 
dance with the provisions of 250.134, to which the equip- 
ment grounding conductors of the branch circuits shall be 



connected. Where the feeder supplies a separate building or 
structure, the requirements of 250.32(B) shall apply. 

215.7 Ungrounded Conductors Tapped from Grounded 

Systems. Two-wire dc circuits and ac circuits of two or more 
ungrounded conductors shall be permitted to be tapped from 
the ungrounded conductors of circuits having a grounded neu- 
tral conductor. Switching devices in each tapped circuit shall 
have a pole in each ungrounded conductor. 

215.9 Ground-Fault Circuit-Interrupter Protection for 
Personnel. Feeders supplying 15- and 20-ampere recep- 
tacle branch circuits shall be permitted to be protected by a 
ground-fault circuit interrupter in lieu of the provisions for 
such interrupters as specified in 210.8 and 590.6(A). 

215.10 Ground-Fault Protection of Equipment. Each 
feeder disconnect rated 1000 amperes or more and installed 
on solidly grounded wye electrical systems of more than 
150 volts to ground, but not exceeding 600 volts phase-to- 
phase, shall be provided with ground-fault protection of 
equipment in accordance with the provisions of 230.95. 

Informational Note: For buildings that contain health care 
occupancies, see the requirements of 517.17. 

Exception No. 1: The provisions of this section shall not 
apply to a disconnecting means for a continuous industrial 
process where a nonorderly shutdown will introduce addi- 
tional or increased hazards. 

Exception No. 2: The provisions of this section shall not 
apply if ground-fault protection of equipment is provided on 
the supply side of the feeder and on the load side of any 
transformer supplying the feeder. 

215.11 Circuits Derived from Autotransformers. Feed- 
ers shall not be derived from autotransformers unless the 
system supplied has a grounded conductor that is electri- 
cally connected to a grounded conductor of the system sup- 
plying the autotransformer. 

Exception No. 1: An autotransformer shall be permitted 
without the connection to a grounded conductor where trans- 
forming from a nominal 208 volts to a nominal 240-volt sup- 
ply or similarly from 240 volts to 208 volts. 

Exception No. 2: In industrial occupancies, where condi- 
tions of maintenance and supervision ensure that only 
qualified persons service the installation, autotransformers 
shall be permitted to supply nominal 600-volt loads from 
nominal 480-volt systems, and 480-volt loads from, nominal 
600-volt systems, without the connection to a similar grounded 
conductor. 

215.12 Identification for Feeders. 

(A) Grounded Conductor. The grounded conductor of a 
feeder shall be identified in accordance with 200.6. 



70-60 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.14 



(B) Equipment Grounding Conductor. The equipment 
grounding conductor shall be identified in accordance with 
250.119. 

(C) Ungrounded Conductors. Where the premises wiring 
system has feeders supplied from more than one nominal 
voltage system, each ungrounded conductor of a feeder 
shall be identified by phase or line and system at all termi- 
nation, connection, and splice points. The means of identi- 
fication shall be permitted to be by separate color coding, 
marking tape, tagging, or other approved means. The 
method utilized for conductors originating within each 
feeder panel board or similar feeder distribution equipment 
shall be documented in a manner that is readily available or 
shall be permanently posted at each feeder panelboard or 
similar feeder distribution equipment. 



ARTICLE 220 
Branch-Circuit, Feeder, and Service 

Calculations 

I. General 

220.1 Scope. This article provides requirements for calcu- 
lating branch-circuit, feeder, and service loads. Part I pro- 
vides for general requirements for calculation methods. Part II 
provides calculation methods for branch-circuit loads. Parts III 
and IV provide calculation methods for feeders and services. 
Part V provides calculation methods for farms. 

Informational Note: See Figure 220.1 for information on 
the organization of Article 220. 

220.3 Application of Other Articles. In other articles ap- 
plying to the calculation of loads in specialized applications, 
there are requirements provided in Table 220.3 that are in 
addition to, or modifications of, those within this article. 

220.5 Calculations. 

(A) Voltages. Unless other voltages are specified, for pur- 
poses of calculating branch-circuit and feeder loads, nomi- 
nal system voltages of 120, 120/240, 208Y/120, 240, 347, 
480Y/277, 480, 600Y/347, and 600 volts shall be used. 

(B) Fractions of an Ampere. Calculations shall be perm;!' ■ 
ted to be rounded to the nearest whole ampere, with deci- 
mal fractions smaller than 0.5 dropped. 

II. Branch-Circuit Load Calculations 

220.10 General. Branch-circuit loads shall be calculated 
as shown in 220.12, 220.14, and 220.16. 



Part 1 General 






Part II Branch-circuit load calculations 






















Part III 
Feeder and 
service load 
calculations 








Part IV 

Optional 

feeder and 

service load 

calculations 








220.61 
Neutral 
Loads 




























1 r 

i 




i 








Farm dwellings 
only 




Farm dwellings 
only 








■ 
i 
i 




i 




Part V Farm load calculations 



Figure 220.1 Branch-Circuit, Feeder, and Service Calculation 
Methods. 



220.12 Lighting Load for Specified Occupancies. A unit 
load of not less than that specified in Table 220.12 for 
occupancies specified therein shall constitute the minimum 
lighting load. The floor area for each floor shall be calcu- 
lated from the outside dimensions of the building, dwelling 
unit, or other area involved. For dwelling units, the calcu- 
lated floor area shall not include open porches, garages, or 
unused or unfinished spaces not adaptable for future use. 

Informational Note: The unit values herein are based on 
minimum load conditions and 100 percent power factor and 
may not provide sufficient capacity for the installation 
contemplated. 

220.14 Other Loads — All Occupancies. In all occupan- 
cies, the minimum load for each outlet for general-use re- 
ceptacles and outlets not used for general illumination shall 
not be less than that calculated in 220.14(A) through (L), 
the loads shown being based on nominal branch-circuit 
voltages. 

Exception: The loads of outlets serving switchboards and 
switching frames in telephone exchanges shall be waived 
from the calculations. 

(A) Specific Appliances or Loads. An outlet for a specific 
appliance or other load not covered in 220. 1 4(B) through 
(L) shall be calculated based on the ampere rating of the 
appliance or load served. 

(B) Electric Dryers and Electric Cooking Appliances in 
Dwelling Units. Load calculations shall be permitted as 
specified in 220.54 for electric dryers and in 220.55 for 
electric ranges and other cooking appliances. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-61 



220.14 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



Table 220.3 Additional Load Calculation References 



Calculation 



Air-conditioning and refrigerating equipment, 

branch-circuit conductor sizing 
Cranes and hoists, rating and size of conductors 
Electric welders, ampacity calculations 
Electrically driven or controlled irrigation 

machines 
Electrified truck parking space 
Electrolytic cell lines 

Electroplating, branch-circuit conductor sizing 
Elevator feeder demand factors 
Fire pumps, voltage drop (mandatory calculation) 
Fixed electric heating equipment for pipelines and 

vessels, branch-circuit sizing 
Fixed electric space-heating equipment, 

branch-circuit sizing 
Fixed outdoor electric deicing and snow-melting 

equipment, branch-circuit sizing 
Industrial machinery, supply conductor sizing 
Marinas and boatyards, feeder and service load 

calculations 
Mobile homes, manufactured homes, and mobile 
home parks, total load for determining power 
supply 
Mobile homes, manufactured homes, and mobile 
home parks, allowable demand factors for park 
electrical wiring systems 
Motion picture and television studios and similar 
locations - sizing of feeder conductors for 
television studio sets 
Motors, feeder demand factor 
Motors, multimotor and combination-load 

equipment 
Motors, several motors or a motor(s) and other 

load(s) 
Over 600-volt branch-circuit calculations 
Over 600-volt feeder calculations 
Phase converters, conductors 
Recreational vehicle parks, basis of calculations 
Sensitive electrical equipment, voltage drop 

(mandatory calculation) 
Solar photovoltaic systems, circuit sizing and 

current 
Storage-type water heaters 
Theaters, stage switchboard feeders 




Section (or Part) 



Part IV 

610.14 
630.1 1, 630.31 

675.7(A), 675.22(A) 



668.3(C) 
669.5 
620.14 
695.7 
427.4 

424.3 

426.4 

670.4(A) 
555.12 

550.18(B) 
550.31 
530.19 



430.26 
430.25 

430.24 

210.19(B) 

215.2(B) 

455.6 

551.73(A) 
647.4(D) 

690.8 

422.11(E) 
520.27 



(C) Motor Loads. Outlets for motor loads shall be calcu- 
lated in accordance with the requirements in 430.22, 430.24, 
and 440.6. 

(D) Luminaires. An outlet supplying luminaire(s) shall be 
calculated based on the maximum volt-ampere rating of the 
equipment and lamps for which the luminaire(s) is rated. 

(E) Heavy-Duty Landholders. Outlets for heavy-duty 
lampholders shall be calculated at a minimum of 600 volt- 
amperes. 



(F) Sign and Outline Lighting. Sign and outline lighting 
outlets shall be calculated at a minimum of 1200 volt- 
amperes for each required branch circuit specified in 
600.5(A). 

(G) Show Windows. Show windows shall be calculated in 
accordance with either of the following- 

(1) The unit load per outlet as required in other provisions 
of this section 

(2) At 200 volt-amperes per 300 mm (1 ft) of show window 



70-62 



NATIONAL ELECTRICAL CODE 201 ! Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.18 



Table 220.12 General Lighting Loads by Occupancy 







Unit Load 




Volt-Amperes/ 


Volt-Amperes/ 


Type of Occupancy 


Square Meter 


Square Foot 


Armories and auditoriums 


11 




1 


Banks 


39 b 




3'/2 b 


Barber shops and beauty 


33 




3 


parlors 








Churches 


11 




1 


Clubs 


22 




2 


Court rooms 


22 




2 


Dwelling units 1 ' 


33 




3 


Garages — commercial 


6 




Vi 


(storage) 








Hospitals 


22 




2 


Hotels and motels, including 


22 




2 


apartment houses without 








provision for cooking by 








tenants" 








Industrial commercial (loft) 


22 




2 


buildings 








Lodge rooms 


17 




VA 


Office buildings 


39 b 




VA h 


Restaurants 


22 




2 


Schools 


33 




3 


Stores 


33 




3 


Warehouses (storage) 


3 




'A 


In any of the preceding 








occupancies except 








one-family dwellings and 








individual dwelling units of 








two-family and multifamily 








dwellings: 








Assembly halls and 


11 




1 


auditoriums 








Halls, corridors, closets, 


6 




'A 


stairways 








Storage spaces 


3 




'/4 



a See220.14(J). 
b See220.14(K). 



(H) Fixed Multioutlet Assemblies. Fixed multioutlet as- 
semblies used in other than dwelling units or the guest 
rooms or guest suites of hotels or motels shall be calculated 
in accordance with (H)(1) or (H)(2). For the purposes of 
this section, the calculation shall be permitted to be based 
on the portion that contains receptacle outlets. 

(1) Where appliances are unlikely to be used simulta- 
neously, each 1.5 m (5 ft) or fraction thereof of each 
separate and continuous length shall be considered as 
one outlet of not less than 1 80 volt-amperes. 

(2) Where appliances are likely to be used simultaneously, 
each 300 mm (1 ft) or fraction thereof shall be consid- 
ered as an outlet of not less than 180 volt-amperes. 

(I) Receptacle Outlets. Except as covered in 220.14(J) 
and (K), receptacle outlets shall be calculated at not less 



than 180 volt-amperes for each single or for each multiple 
receptacle on one yoke. A single piece of equipment consist- 
ing of a multiple receptacle comprised of four or more recep- 
tacles shall be calculated at not less than 90 volt-amperes per 
receptacle. This provision shall not be applicable to the recep- 
tacle outlets specified in 210.11(C)(1) and (C)(2). 

(J) Dwelling Occupancies. In one-family, two-family, and 
multifamily dwellings and in guest rooms or guest suites of 
hotels and motels, the outlets specified in (J)(l), (J)(2), and 
(J)(3) are included in the general lighting load calculations 
of 220.12. No additional load calculations shall be required 
for such outlets. 

(1) All general-use receptacle outlets of 20-ampere rating 
or less, including receptacles connected to the circuits 
in 210.11(C)(3) 

(2) The receptacle outlets specified in 210.52(E) and (G) 

(3) The lighting outlets specified in 210.70(A) and (B) 

(K) Banks and Office Buildings. In banks or office build- 
ings, the receptacle loads shall be calculated to be the larger 
of (1) or (2): 

(1) The calculated load from 220.14(1) 

(2) 11 volt-amperes/m 2 or 1 volt- ampere/ft 2 

(L) Other Outlets. Other outlets not covered in 220.14(A) 
through (K) shall be calculated based on 1 80 volt-amperes 
per outlet. 

220.16 Loads for Additions to Existing Installations. 

(A) Dwelling Units. Loads added to an existing dwelling 
unit(s) shall comply with the following as applicable: 

(1) Loads for structural additions to an existing dwelling unit 
or for a previously unwired portion of an existing dwell- 
ing unit, either of which exceeds 46.5 m 2 (500 ft 2 ), shall 
be calculated in accordance with 220.12 and 220.14. 

(2) Loads for new circuits or extended circuits in previ- 
ously wired dwelling units shall be calculated in accor- 
dance with either 220.12 or 220.14, as applicable. 

(B) Other Than Dwelling Units. Loads for new circuits 
or extended circuits in other than dwelling units shall be 
calculated in accordance with either 220.12 or 220.14, as 
applicable. 

220.18 Maximum Loads. The total load shall not exceed 
the rating of the branch circuit, and it shall not exceed the 
maximum loads specified in 220.18(A) through (C) under 
the conditions specified therein. 

(A) Motor-Operated and Combination Loads. Where a 
circuit supplies only motor-operated loads, Article 430 shall 
apply. Where a circuit supplies only air-conditioning equip- 
ment, refrigerating equipment, or both, Article 440 shall apply. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-63 



220.4(1 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



For circuits supplying loads consisting of motor-operated uti- 
lization equipment that is fastened in place and has a motor 
larger than Vs hp in combination with other loads, the total 
calculated load shall be based on 125 percent of the largest 
motor load plus the sum of the other loads. 

(B) Inductive and LED Lighting Loads. For circuits sup- 
plying lighting units that have ballasts, transformers, au- 
totransformers, or !.l;15 drivers, the calculated load shall be 
based on the total ampere ratings of such units and not on 
the total watts of the lamps. 

(C) Range Loads. It shall be permissible to apply demand 
factors for range loads in accordance with Table 220.55, 
including Note 4. 

III. Feeder and Service Load Calculations 

220.40 General. The calculated load of a feeder or service 
shall not be less than the sum of the loads on the branch 
circuits supplied, as determined by Part II of this article, 
after any applicable demand factors permitted by Part III or 
IV or required by Part V have been applied. 

Informational Note: See Examples Dl(a) through D10 in 
Informative Annex D. See 220.1 8(B) for the maximum load 
in amperes permitted for lighting units operating at less 
than 1.00 percent power factor. 

220.42 General Lighting. The demand factors specified in 
Table 220.42 shall apply to that portion of the total branch- 
circuit load calculated for general illumination. They shall 
not be applied in determining the number of branch circuits 
for general illumination. 

220.43 Show- Window and Track Lighting. 

(A) Show Windows. For show-window lighting, a load of 
not less than 660 volt-amperes/linear meter or 200 volt- 
amperes/linear foot shall be included for a show window, 
measured horizontally along its base. 

Informational Note: See 220.14(G) for branch circuits 
supplying show windows. 

(B) Track Lighting. For track lighting in other than dwell- 
ing units or guest rooms or guest suites of hotels or motels, 
an additional load of 150 volt-amperes shall be included for 
every 600 mm (2 ft) of lighting track or fraction thereof. 
Where multicircuit track is installed, the load shall be con- 
sidered to be divided equally between the track circuits. 

Exception: If the track lighting is supplied through a de- 
vice that limits the current to the track, the load shall be 
permitted to he calculated based on the rating of the device 
used to limit the current. 



Table 220.42 Lighting Load Demand Factors 





Portion of Lighting 






Load to Which 






Demand Factor 




Type of 


Applies 


Demand Factor 


Occupancy 


(Volt-Amperes) 


(%) 


Dwelling units 


First 3000 or less at 
From 3001 to 


100 




120,000 at 


35 




Remainder over 






120,000 at 


25 



Hospitals* 



First 50,000 or less at 
Remainder over 
50,000 at 



40 



20 



Hotels and motels, 
including 
apartment houses 
without provision 
for cooking by 
tenants* 



First 20,000 or less at 


50 


From 20,001 to 




100,000 at 


40 


Remainder over 




100,000 at 


30 



Warehouses First 12,500 or less at 100 

(storage) Remainder over 

12,500 at 50 



All others 



Total volt-amperes 



100 



"The demand factors of this table shall not apply to the calculated load 
of feeders or services supplying areas in hospitals, hotels, and motels 
where the entire lighting is likely to be used at one time, as in oper- 
ating rooms, ballrooms, or dining rooms. 



220.44 Receptacle Loads — Other Than Dwelling 
Units. Receptacle loads calculated in accordance with 
220.14(H) and (I) shall be permitted to be made subject to 
the demand factors given in Table 220.42 or Table 220.44. 



Table 220.44 Demand Factors for Non-Dwelling Receptacle 
Loads 



Portion of Receptacle Load to Which 

Demand Factor Applies Demand Factor 

(Volt-Amperes) (%) 



First 10 kVA or less at 
Remainder over 1 kVA at 



100 

50 



220.50 Motors. Motor loads shall be calculated in accor- 
dance with 430.24, 430.25, and 430.26 and with 440.6 for 
hermetic refrigerant motor compressors. 

220.51 Fixed Electric Space Heating. Fixed electric 
space-heating loads shall be calculated at 100 percent of the 
total connected load. However, in no case shall a feeder or 
service load current rating be less than the rating of the 
largest branch circuit supplied. 



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NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.60 



Exception: Where reduced loading of the conductors re- 
sults from units operating on duty-cycle, intermittently, or 
from all units not operating at the same time, the authority 
having jurisdiction may grant permission for feeder and 
service conductors to have an ampacity less than 100 per- 
cent, provided the conductors have an ampacity for the 
load so determined. 



Table 220.54 Demand Factors for Household Electric 
Clothes Dryers 



220.52 Small-Appliance and Laundry Loads 
ing Unit. 



Dwell- 



(A) Small-Appliance Circuit Load. In each dwelling unit, 
the load shall be calculated at 1500 volt-amperes for each 
2-wire small-appliance branch circuit as covered by 
210.11(C)(1). Where the load is subdivided through two or 
more feeders, the calculated load for each shall include not 
less than 1500 volt-amperes for each 2-wire small- 
appliance branch circuit. These loads shall be permitted to 
be included with the general lighting load and subjected to 
the demand factors provided in Table 220.42. 

Exception: The individual branch circuit permitted by 
210.52(B)(1), Exception No. 2, shall be permitted to be 
excluded from the calculation required by 220.52. 

(B) Laundry Circuit Load. A load of not less than 1500 
volt-amperes shall be included for each 2-wire laundry 
branch circuit installed as covered by 210.11(C)(2). This 
load shall be permitted to be included with the general 
lighting load and subjected to the demand factors provided 
in Table 220.42. 

220.53 Appliance Load — Dwelling Unit(s). It shall be 
permissible to apply a demand factor of 75 percent to the 
nameplate rating load of four or more appliances fastened 
in place, other than electric ranges, clothes dryers, space- 
heating equipment, or air-conditioning equipment, that are 
served by the same feeder or service in a one-family, two- 
family, or multifamily dwelling. 

220.54 Electric Clothes Dryers — Dwelling Unit(s). The 

load for household electric clothes dryers in a dwelling 
unit(s) shall be either 5000 watts (volt-amperes) or the 
nameplate rating, whichever is larger, for each dryer 
served. The use of the demand factors in Table 220.54 shall 
be permitted. Where two or more single-phase dryers are 
supplied by a 3-phase, 4-wire feeder or service, the total 
load shall be calculated on the basis of twice the maximum 
number connected between any two phases. Kilovolt- 
amperes (kVA) shall be considered equivalent to kilowatts 
(kW) for loads calculated in this section. 

220.55 Electric Ranges and Other Cooking Appliances 
— Dwelling Unit(s). The load for household electric 
ranges, wall-mounted ovens, counter-mounted cooking 
units, and other household cooking appliances individually 



Number of 






Demand Factor 


Dryers 








(%) 


1-4 








100 


5 








85 


6 








75 


7 








65 


8 








60 


9 








55 


10 








50 


11 








47 


12-23 


47% 


minus 


i 1% 


for each dryer exceeding 1 1 


24-42 


35% i 


minus 


0.5% 


for each dryer exceeding 23 


43 and over 








25% 



rated in excess of 1% kW shall be permitted to be calcu- 
lated in accordance with Table 220.55. Kilovolt-amperes 
(kVA) shall be considered equivalent to kilowatts (kW) for 
loads calculated under this section. 

Where two or more single-phase ranges are supplied by 
a 3-phase, 4-wire feeder or service, the total load shall be 
calculated on the basis of twice the maximum number con- 
nected between any two phases. 

Informational Note No. 1: See Example D5(A) in Infor- 
mative Annex D. 

Informational Note No. 2: See Table 220.56 for commer- 
cial cooking equipment. 

Informational Note No. 3: See the examples in Informa- 
tive Annex D. 

220.56 Kitchen Equipment — Other Than Dwelling 

Unit(s). It shall be permissible to calculate the load for 
commercial electric cooking equipment, dishwasher 
booster heaters, water heaters, and other kitchen equipment 
in accordance with Table 220.56. These demand factors 
shall be applied to all equipment that has either thermo- 
static control or intermittent use as kitchen equipment. 
These demand factors shall not apply to space-heating, ven- 
tilating, or air-conditioning equipment. 

However, in no case shall the feeder or service calcu- 
lated load be less than the sum of the largest two kitchen 
equipment loads. 

220.60 Noncoincident Loads. Where it is unlikely that 
two or more noncoincident loads will be in use simulta- 
neously, it shall be permissible to use only the largest 
load(s) that will be used at one time for calculating the total 
load of a feeder or service. 



201 1 Edition NATIONAL ELECTRICAL CODE 



70-65 



220.60 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER AND SERVICE CALCULATIONS 



Table 220.55 Demand Factors and Loads for Household Electric Ranges, Wall-Mounted Ovens, Counter-Mounted Cooking 
Units, and Other Household Cooking Appliances over VA kW Rating (Column C to be used in all cases except as otherwise 
permitted in Note 3.) 



Demand Factor (%) (See Notes) 



Number of Appliances 



Column A 
(Less than 3Vi kW Rating) 



Column B 

(3'/2 kW through 8 3 A kW 

Rating) 



Column C 

Maximum Demand (kW) (See 

Notes) (Not over 12 kW Rating) 



80 
75 
70 
66 

62 



80 
65 

55 
50 
45 



II 

14 
17 
20 



59 
56 
53 
51 
49 



43 
40 
36 

35 

34 



21 

22 
23 
24 
25 



11 
12 
13 
14 
15 



47 
45 
43 
41 
40 



32 
32 
32 
32 
32 



26 
27 
28 
29 
30 



16 

17 
18 
19 
20 



39 
38 

37 
36 
35 



28 
28 
28 
28 
28 



31 
32 
33 
34 
35 



21 

22 
23 
24 
25 



34 
33 
32 
31 
30 



26 
26 
26 
26 
26 



36 
37 
38 
39 
40 



26-30 
3 1—40 



30 
30 



24 

22 



1 5 kW + 1 kW for each range 



41-50 

51-60 

61 and over 



30 
30 
30 



20 
18 
16 



25 kW + % kW for each range 



Notes: 

1 . Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 1 2 kW but not more than 27 kW, the maximum 
demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual 
ranges exceeds 12 kW. 

2. Over & 3 A kW through 27 kW ranges of unequal ratings. For ranges individually rated more than S 3 A kW and of different ratings, but none 
exceeding 27 kW, an average value of rating shall be calculated by adding together the ratings of all ranges to obtain the total connected load (using 
1 2 kW for any range rated less than 1 2 kW) and dividing by the total number of ranges. Then the maximum demand in Column C shall be increased 
5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12 kW. 

3. Over VA kW through & 3 A kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household 
cooking appliances rated more than VA kW but not more than $ 3 A kW and multiply the sum by the demand factors specified in Column A or 
Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand 
factors for each column shall be applied to the appliances for that column, and the results added together. 

4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch- 
circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load 
for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same 
room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range. 

5. This table shall also apply to household cooking appliances rated over VA kW and used in instructional programs. 



70-66 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.82 



Table 220.56 Demand Factors for Kitchen Equipment 
Other Than Dwelling Unit(s) 



Number of Units of 


Demand Factor 


Equipment 


(%) 


1 


100 


2 


100 


3 


90 


4 


80 


5 


70 


6 and over 


65 



220.61 Feeder or Service Neutral Load. 

(A) Basic Calculation. The feeder or service neutral load 
shall be the maximum unbalance of the load determined by 
this article. The maximum unbalanced load shall be the 
maximum net calculated load between the neutral conduc- 
tor and any one ungrounded conductor. 

Exception: For 3-wire, 2-phase or 5-wire, 2-phase sys- 
tems, the maximum unbalanced load shall be the maximum 
net calculated load between the neutral conductor and any 
one ungrounded conductor multiplied by 140 percent. 

(B) Permitted Reductions. A service or feeder supplying 
the following loads shall be permitted to have an additional 
demand factor of 70 percent applied to the amount in 
220.61(B)(1) or portion of the amount in 220.61(B)(2) de- 
termined by the basic calculation: 

(1) A feeder or service supplying household electric ranges, 
wall-mounted ovens, counter-mounted cooking units, and 
electric dryers, where the maximum unbalanced load has 
been determined in accordance with Table 220.55 for 
ranges and Table 220.54 for dryers 

(2) That portion of the unbalanced load in excess of 200 am- 
peres where the feeder or service is supplied from a 
3-wire dc or single-phase ac system; or a 4- wire, 3-phase, 
3-wire, 2-phase system; or a 5-wire, 2-phase system 

(C) Prohibited Reductions. There shall be no reduction of 
the neutral or grounded conductor capacity applied to the 
amount in 220.61(C)(1), or portion of the amount in (C)(2), 
from that determined by the basic calculation: 

(1) Any portion of a 3-wire circuit consisting of 2 un- 
grounded conductors and the neutral conductor of a 
4-wire, 3-phase, wye-connected system 

(2) That portion consisting of nonlinear loads supplied 
from a 4-wire, wye-connected, 3-phase system 

Informational Note No. 1: See Examples Dl(a), Dl(b), 
D2(b), D4(a), and D5(a) in Informative Annex D. 

Informational Note No. 2: A 3-phase, 4-wire, wye-connected 
power system used to supply power to nonlinear loads may 
necessitate that the power system design allow for the possi- 
bility of high harmonic neutral-conductor currents. 



IV. Optional Feeder and Service Load Calculations 

220.80 General. Optional feeder and service load calcula- 
tions shall be permitted in accordance with Part IV. 

220.82 Dwelling Unit. 

(A) Feeder and Service Load. This section applies to a 
dwelling unit having the total connected load served by a 
single 120/240-volt or 208Y/120-volt set of 3-wire service 
or feeder conductors with an ampacity of 100 or greater. It 
shall be permissible to calculate the feeder and service 
loads in accordance with this section instead of the method 
specified in Part III of this article. The calculated load shall 
be the result of adding the loads from 220.82(B) and (C). 
Feeder and service-entrance conductors whose calculated 
load is determined by this optional calculation shall be per- 
mitted to have the neutral load determined by 220.61. 

(B) General Loads. The general calculated load shall be 
not less than 100 percent of the first 10 kVAplus 40 percent 
of the remainder of the following loads: 

(1) 33 volt-amperes/m 2 or 3 volt-amperes/ft 2 for general 
lighting and general-use receptacles. The floor area for 
each floor shall be calculated from the outside dimen- 
sions of the dwelling unit. The calculated floor area 
shall not include open porches, garages, or unused or 
unfinished spaces not adaptable for future use. 

(2) 1500 volt-amperes for each 2- wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit covered in 210.11(C)(1) and (C)(2). 

(3) The nameplate rating of the following: 

a. All appliances that are fastened in place, permanently 
connected, or located to be on a specific circuit 

b. Ranges, wall-mounted ovens, counter-mounted cook- 
ing units 

c. Clothes dryers that are not connected to the laundry 
branch circuit specified in item (2) 

d. Water heaters 

(4) The nameplate ampere or kVA rating of all permanently 
connected motors not included in item (3). 

(C) Heating and Air-Conditioning Load. The largest of 
the following six selections (load in kVA) shall be included: 

(1 ) 100 percent of the nameplate rating(s) of the air condi- 
tioning and cooling. 

(2) 100 percent of the nameplate rating(s) of the heat pump 
when the heat pump is used without any supplemental 
electric heating. 

(3) 100 percent of the nameplate rating(s) of the heat pump 
compressor and 65 percent of the supplemental electric 
heating for central electric space-heating systems. If the 
heat pump compressor is prevented from operating at 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-67 



220.83 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



the same time as the supplementary heat, it does not 
need to be added to the supplementary heat for the total 
central space heating load. 

(4) 65 percent of the nameplate rating(s) of electric space 
heating if less than four separately controlled units. 

(5) 40 percent of the nameplate rating(s) of electric space 
heating if four or more separately controlled units. 

(6) 100 percent of the nameplate ratings of electric thermal 
storage and other heating systems where the usual load 
is expected to be continuous at the full nameplate 
value. Systems qualifying under this selection shall not 
be calculated under any other selection in 220.82(C). 

220.83 Existing Dwelling Unit. This section shall be per- 
mitted to be used to determine if the existing service or feeder 
is of sufficient capacity to serve additional loads. Where the 
dwelling unit is served by a 120/240- volt or 208Y/120-volt, 
3-wire service, it shall be permissible to calculate the total load 
in accordance with 220.83(A) or (B). 

(A) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is Not to Be In- 
stalled. The following percent ires shall be used for exist- 
ing and additional new loads. 



Load 



Percent of Load 



Air-conditioning equipment 
Central electric space heating 
Less than four separately 

controlled space-heating units 
First 8 kVA of all other loads 
Remainder of all other loads 



100 
100 
100 

100 

40 



Other loads shall include the following: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m 2 or 3 volt-amperes/ft 2 as determined by 
220.12 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit covered in 210.11(C)(1) and (C)(2) 

(3) The nameplate rating of the following: 

a. All appliances that are fastened in place, permanently 
connected, or located to be on a specific circuit 

b. Ranges, wall-mounted ovens, counter-mounted cook- 
ing units 

c. Clothes dryers that are not connected to the laundry 
branch circuit specified in (2) 

d. Water heaters 



Load (kVA) 



Percent of Load 



First 8 kVA of load at 
Remainder of load at 



100 

40 



Load calculations shall include the following: 

(1) General lighting and general-use receptacles at 33 volt- 
amperes/m 2 or 3 volt-amperes/ft 2 as determined by 

220.12 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit covered in 210.11(C)(1) and (C)(2) 

(3) The nameplate rating of the following: 

a. All appliances that are fastened in place, permanently 
connected, or located to be on a specific circuit 

b. Ranges, wall-mounted ovens, counter-mounted cook- 
ing units 

c. Clothes dryers that are not connected to the laundry 
branch circuit specified in item (2) 

d. Water heaters 

(B) Where Additional Air-Conditioning Equipment or 
Electric Space-Heating Equipment Is to Be Installed. 

The following percentages shall be used for existing and 
additional new loads. The larger connected load of air- 
conditioning or space-heating, but not both, shall be used. 



220.84 Multifamily Dwelling. 

(A) Feeder or Service Load. It shall be permissible to 
calculate the load of a feeder or service that supplies three 
or more dwelling units of a multifamily dwelling in accor- 
dance with Table 220.84 instead of Part III of this article if 
all the following conditions are met: 

(1) No dwelling unit is supplied by more than one feeder. 

(2) Each dwelling unit is equipped with electric cooking 
equipment. 

Exception: When the calculated load for multifamily dwell- 
ings without electric cooking in Part III of this article ex- 
ceeds that calculated under Part IV for the identical load 
plus electric cooking (based on 8 kW per unit), the lesser of 
the two loads shall be permitted to be used. 

(3) Each dwelling unit is equipped with either electric space 
heating or air conditioning, or both. Feeders and service 
conductors whose calculated load is determined by this 
optional calculation shall be permitted to have the neutral 
load determined by 220.61. 

(B) House Loads. House loads shall be calculated in ac- 
cordance with Part III of this article and shall be in addition 
to the dwelling unit loads calculated in accordance with 
Table 220.84. 



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NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



220.87 



Table 220.84 Optional Calculations — Demand Factors for 
Three or More Multifamily Dwelling Units 



Number of 
Dwelling Units 



Demand Factor 

(%) 



3-5 
6-7 
8-10 



45 
44 
43 



11 
12-13 
14-15 
16-17 
18-20 



42 
41 
40 
39 
38 



21 
22-23 
24-25 
26-27 
28-30 



37 
36 
35 
34 
33 



31 

32-33 
34-36 
37-38 
39^12 



32 
31 
30 
29 
28 



43-45 
46-50 
51-55 
56-61 
62 and over 



27 
26 

25 
24 
23 



(C) Calculated Loads. The calculated load to which the 
demand factors of Table 220.84 apply shall include the 
following: 

(1) 33 volt-amperes/m 2 or 3 volt-amperes/ft 2 for general 
lighting and general-use receptacles 

(2) 1500 volt-amperes for each 2-wire, 20-ampere small- 
appliance branch circuit and each laundry branch cir- 
cuit covered in 210.11(C)(1) and (C)(2) 

(3) The nameplate rating of the following: 

a. All appliances that are fastened in place, permanently 
connected, or located to be on a specific circuit 

b. Ranges, wall-mounted ovens, counter-mounted cook- 
ing units 

c. Clothes dryers that are not connected to the laundry 
branch circuit specified in item (2) 

d. Water heaters 

(4) The nameplate ampere or kVA rating of all perma- 
nently connected motors not included in item (3) 

(5) The larger of the air-conditioning load or the fixed elec- 
tric space-heating load 

220.85 Two Dwelling Units. Where two dwelling units 
are supplied by a single feeder and the calculated load 



under Part III of this article exceeds that for three identical 
units calculated under 220.84, the lesser of the two loads 
shall be permitted to be used. 

220.86 Schools. The calculation of a feeder or service load 
for schools shall be permitted in accordance with Table 220.86 
in lieu of Part III of this article where equipped with electric 
space heating, air conditioning, or both. The connected load to 
which the demand factors of Table 220.86 apply shall include 
all of the interior and exterior lighting, power, water heating, 
cooking, other loads, and the larger of the air-conditioning 
load or space-heating load within the building or structure. 

Feeders and service conductors whose calculated load 
is determined by this optional calculation shall be permitted 
to have the neutral load determined by 220.61. Where the 
building or structure load is calculated by this optional 
method, feeders within the building or structure shall have 
ampacity as permitted in Part III of this article; however, 
the ampacity of an individual feeder shall not be required to 
be larger than the ampacity for the entire building. 

This section shall not apply to portable classroom 
buildings. 



Table 220.86 Optional Method — Demand Factors for 
Feeders and Service Conductors for Schools 







Demand 






Factor 


Connected Load 


(Percent) 


First 33 VA/m 2 


(3 VA/ft 2 ) at 


100 


Plus, 






( her 33 through lln 


(3 through 20 VA/ft 2 ) 


75 


VA/m 2 


at 




Plus, 






Remainder over 220 


(20 VA/ft 2 ) at 


25 


VA/m 2 







220.87 Determining Existing Loads. The calculation of a 
feeder or service load for existing installations shall be 
permitted to use actual maximum demand to determine the 
existing load under all of the following conditions: 
(1) The maximum demand data is available for a 1-year 
period. 

Exception: If the maximum demand data for a 1 -year pe- 
riod is not available, the calculated load shall be permitted 
to be based on the maximum demand (measure of average 
power demand over a 15 -minute period) continuously re- 
corded over a minimum 30-day period using a recording 
ammeter or power meter connected to the highest loaded 
phase of the feeder or service, based on the initial loading 
at the start of the recording. The recording shcdl reflect the 
maximum demand of the feeder or service by being taken 
when the building or space is occupied and shall include by 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-69 



22(1.88 



ARTICLE 220 — BRANCH-CIRCUIT, FEEDER, AND SERVICE CALCULATIONS 



measurement or calculation the larger of the heating or 
cooling equipment load, and other loads that may be peri- 
odic in nature due to seasonal or similar conditions. 

(2) The maximum demand at 125 percent plus the new 
load does not exceed the ampacity of the feeder or 
rating of the service. 

(3) The feeder has overcurrent protection in accordance 
with 240.4, and the service has overload protection in 
accordance with 230.90. 

220.88 New Restaurants. Calculation of a service or feeder 
load, where the feeder serves the total load, for a new restau- 
rant shall be permitted in accordance with Table 220.88 in lieu 
of Part III of this article. 

The overload protection of the service conductors shall 
be in accordance with 230.90 and 240.4. 

Feeder conductors shall not be required to be of greater 
ampacity than the service conductors. 

Service or feeder conductors whose calculated load is 
determined by this optional calculation shall be permitted 
to have the neutral load determined by 220.61 . 

V. Farm Load Calculations 

220.100 General. Farm loads shall be calculated in accor- 
dance with Part V. 

220.102 Farm Loads — Buildings and Other Loads. 

(A) Dwelling Unit. The feeder or service load of a farm 
dwelling unit shall be calculated in accordance with the 
provisions for dwellings in Part III or IV of this article. 
Where the dwelling has electric heat and the farm has elec- 
tric grain-drying systems, Part IV of this article shall not be 
used to calculate the dwelling load where the dwelling and 
farm loads are supplied by a common service. 

(B) Other Than Dwelling Unit. Where a feeder or service 
supplies a farm building or other load having two or more 
separate branch circuits, the load for feeders, service conduc- 
tors, and service equipment shall be calculated in accordance 
with demand factors not less than indicated in Table 220.102. 



Table 220.102 Method for Calculating Farm Loads for 
Other Than Dwelling Unit 



Ampere Load at 240 Volts Maximum 



Demand Factor 



The greater ni the following: 

All loads that are expected to operate 100 

simultaneously, or 
125 percent of the full loud current of 

tiii lar ■" ii oio ot 

First 60 amperes of the load 
Next 60 amperes of all other loads 50 

Remainder of other loads 25 



220.103 Farm Loads — Total. Where supplied by a com- 
mon service, the total load of the farm for service conduc- 
tors and service equipment shall be calculated in accor- 
dance with the farm dwelling unit load and demand factors 
specified in Table 220.103. Where there is equipment in 
two or more farm equipment buildings or for loads having 
the same function, such loads shall be calculated in accor- 
dance with Table 220.102 and shall be permitted to be 
combined as a single load in Table 220.103 for calculating 
the total load. 



Table 220.103 Method for Calculating Total Farm Load 



Individual Loads Calculated in 
Accordance with Table 220.102 



Demand Factor 

(%) 



Largest load 
Second largest load 
Third largest load 
Remaining loads 



100 
75 
65 
50 



Note: To this total load, add the load of the farm dwelling unit calcu- 
lated in accordance with Part III or IV of this article. Where the 
dwelling has electric heat and the farm has electric grain-drying sys- 
tems, Part IV of this article shall not be used to calculate the dwelling 
load. 



Table 220.88 Optional Method — Permitted Load Calculations for Service and Feeder Conductors for New Restaurants 



Total Connected 
Load (kVA) 


All Electric Restaurant 
Calculated Loads (kVA) 


Not All Electric Restaurant 
Calculated Loads (kVA) 




0-200 
201-325 
326-800 
Over 800 


80% 
10% (amount over 200) + 160.0 
50% (amount over 325) + 172.5 
50% (amount over 800) + 410.0 


100% 
50% (amount over 200) + 200.0 
45% (amount over 325) + 262.5 
20% (amount over 800) + 476.3 





Note: Add all electrical loads, including both heating and cooling loads, to calculate the total connected load. Select the one demand factor that 
applies trom the table, then multiply the total connected load by this single demand factor. 



70-70 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.7 



Table 225.3 Other Articles 



ARTICLE 225 
Outside Branch Circuits and Feeders 



225.1 Scope. This article covers requirements for outside 
branch circuits and feeders run on or between buildings, 
structures, or poles on the premises; and electrical equip- 
ment and wiring for the supply of utilization equipment that 
is located on or attached to the outside of buildings, struc- 
tures, or poles. 

Informational Note: For additional information on wiring 
over 600 volts, see ANSI C2-2007, National Electrical 
Safety Code. 

225.2 Definition. 

Substation. An enclosed as .■ gc oi jquipmcnl (t ■• 

switches, circuit breakers Hum's and transformers) Under 
the control of qualified persons through winch electric en- 
ergy is p-iv.rtl foi th« I'tnpo v ol witching oi m )ihi ing its' 
characteristics. 

225.3 Other Articles. Application of other articles, includ- 
ing additional requirements to specific cases of equipment 
and conductors, is shown in Table 225.3. 

I. General 

225.4 Conductor Covering. Where within 3.0 m (10 ft) of 
any building or structure other than supporting poles or 
towers, open individual (aerial) overhead conductors shall 
be insulated or covered. Conductors in cables or raceways, 
except Type MI cable, shall be of the rubber-covered type 
or thermoplastic type and, in wet locations, shall comply 
with 310.10(C). Conductors for festoon lighting shall be of 
the rubber-covered or thermoplastic type. 

Exception: Equipment grounding conductors and grounded 
circuit conductors shall be permitted to be bare or covered as 
specifically permitted elsewhere in this Code. 

225.5 Size of Conductors 600 Volts, Nominal, or Less. 

The ampacity of outdoor branch-circuit and feeder conduc- 
tors shall be in accordance with 310.15 based on loads as 
determined under 220.10 and Part III of Article 220. 

225.6 Conductor Size and Support. 

(A) Overhead Spans. Open individual conductors shall 

not be smaller than the following: 

(1) For 600 volts, nominal, or less, 10 AWG copper or 
8 AWG aluminum for spans up to 15 m (50 ft) in 
length, and 8 AWG copper or 6 AWG aluminum for a 
longer span unless supported by a messenger wire 



Equipment/Conductors 


Article 


Branch circuits 


210 


Class 1 , Class 2, and Class 3 


725 


remote-control, signaling, and 




power-limited circuits 




Communications circuits 


800 


Community antenna television and radio 


820 


distribution systems 




Conductors for general wiring 


310 


Electrically driven or controlled 


675 


irrigation machines 




Electric signs and outline lighting 


600 


Feeders 


215 


Fire alarm systems 


760 


Fixed outdoor electric deicing and 


426 


snow-melting equipment 




Floating buildings 


553 


Grounding and bonding 


250 


Hazardous (classified) locations 


500 


Hazardous (classified) locations — 


510 


specific 




Marinas and boatyards 


555 


Messenger-supported wiring 


396 


Mobile homes, manufactured homes, 


550 


and mobile home parks 




Open wiring on insulators 


398 


Over 600 volts, general 


490 


Overcurrent protection 


240 


Radio and television equipment 


810 


Services 


230 


Solar photovoltaic systems 


690 


Swimming pools, fountains, and similar 


680 


installations 




Use and identification of grounded 


200 


conductors 





(2) For over 600 volts, nominal, 6 AWG copper or 4 AWG 
aluminum where open individual conductors, and 8 AWG 
copper or 6 AWG aluminum where in cable 

(B) Festoon Lighting. Overhead conductors for festoon 
lighting shall not be smaller than 12 AWG unless the con- 
ductors are supported by messenger wires. In all spans ex- 
ceeding 12 m (40 ft), the conductors shall be supported by 
messenger wire. The messenger wire shall be supported by 
strain insulators. Conductors or messenger wires shall not 
be attached to any fire escape, downspout, or plumbing 
equipment. 

225.7 Lighting Equipment Installed Outdoors. 

(A) General. For the supply of lighting equipment in- 
stalled outdoors, the branch circuits shall comply with Ar- 
ticle 210 and 225.7(B) through (D). 

(B) Common Neutral. The ampacity of the neutral conduc- 
tor shall not be less than the maximum net culeniaied load 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-71 



225.8 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



current between the neutral conductor and all ungrounded 
conductors connected to any one phase of the circuit. 

(C) 277 Volts to Ground. Circuits exceeding 120 volts, 
nominal, between conductors and not exceeding 277 volts, 
nominal, to ground shall be permitted to supply luminaires 
for illumination of outdoor areas of industrial establish- 
ments, office buildings, schools, stores, and other commer- 
cial or public buildings. 

(D) 600 Volts Between Conductors. Circuits exceeding 
277 volts, nominal, to ground and not exceeding 600 volts, 
nominal, between conductors shall be permitted to supply 
the auxiliary equipment of electric-discharge lamps in ac- 
cordance with 210.6(D)(1). 

225.8 Calculation of Loads 600 Volts, Nominal, or ! .ess. 

(A) Branch Circuits. The load on outdooi branch circuits 
shall be as determined b_\ 90 10. 

(B) Feeders. The load on outdoor feeder,-' shall be as de- 
lennined by Fart III of Article 220. 

225.10 Wiring on Buildings. The installation of outside 
wiring on surfaces of buildings shall be permitted for cir- 
cuits of not over 600 volts, nominal, as open wiring on 
insulators, as multiconductor cable, as Type MC cable, as 
Type UF cable, as Type MI cable, as messenger-supported 
wiring, in rigid metal conduit, in intermediate metal con- 
duit, in rigid polyov! > lidind*. (PVC) conduit, in rein- 
forced thermosetting resin com Inn (RTRC). in cable trays, 
as cablebus, in wireways, in auxiliary gutters, in electrical 
metallic tubing, in flexible metal conduit, in liquidtight 
flexible metal conduit, in liquidtight flexible nonmetallic 
conduit, and in busways. Circuits of over 600 volts, nomi- 
nal, shall be installed as provided in 300.37. 

225.11 Circuit Exits and Entrances. Where outside 
branch and feeder circuits leave or enter a building, the 
requirements of 230.52 and 230.54 shall apply. 

225.12 Open-Conductor Supports. Open conductors 
shall be supported on glass or porcelain knobs, racks, 
brackets, or strain insulators. 

225.14 Open-Conductor Spacings. 

(A) 600 Volts, Nominal, or Less. Conductors of 600 volts, 
nominal, or less, shall comply with the spacings provided 
in Table 230.51(C). 

(B) Over 600 Volts, Nominal. Conductors of over 600 volts, 
nominal, shall comply with the spacings provided in 110.36 
and 490.24. 



(C) Separation from Other Circuits. Open conductors 
shall be separated from open conductors of other circuits or 
systems by not less than 100 mm (4 in.). 

(D) Conductors on Poles. Conductors on poles shall have 
a separation of not less than 300 mm (1 ft) where not 
placed on racks or brackets. Conductors supported on poles 
shall provide a horizontal climbing space not less than the 
following: 

(1) Power conductors below communications conductors 

— 750 mm (30 in.) 

(2) Power conductors alone or above communications con- 
ductors: 

a. 300 volts or less — 600 mm (24 in.) 

b. Over 300 volts — 750 mm (30 in.) 

(3) Communications conductors below power conductors 

— same as power conductors 

(4) Communications conductors alone — no requirement 

225.15 Supports over Buildings. Supports over a building 
shall be in accordance with 230.29. 

225.16 Attachment to Buildings. 

(A) Point of Attachment. The point of attachment to a 
building shall be in accordance with 230.26. 

(B) Means of Attachment. The means of attachment to a 
building shall be in accordance with 230.27. 

225.17 Masts as Supports. Where a mast is used for the 
support of final spans of feeders or branch circuits, it shall 
be of adequate strength or be supported by braces or guys to 
withstand safely the strain imposed by the overhead drop. 
Where raceway-type masts are used, all raceway fittings shall 
be identified for use with masts. Only the feeder or branch- 
circuit conductors specified within this section shall be permit- 
ted to be attached to the feeder and/or branch-circuit mast. 

225.18 Clearance for Overhead Conductors and Cables. 

Overhead spans of open conductors and open multiconduc- 
tor cables of not over 600 volts, nominal, shall have a 
clearance of not less than the following: 

(1) 3.0 m (10 ft) — above finished grade, sidewalks, or 
from any platform or projection from which they might 
be reached where the voltage does not exceed 150 volts 
to ground and accessible to pedestrians only 

(2) 3.7 m (12 ft) — over residential property and drive- 
ways, and those commercial areas not subject to truck 
traffic where the voltage does not exceed 300 volts to 
ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m (12-ft) 
classification where the voltage exceeds 300 volts to 
ground 



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ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.26 



(4) 5.5 m (18 ft) — over public streets, alleys, roads, parking 
areas subject to truck traffic, driveways on other than resi- 
dential property, and other land traversed by vehicles, 
such as cultivated, grazing, forest, and orchard 

(5) 7.5 m (24.5 ft) — over track rails of railroads 

225.19 Clearances from Buildings for Conductors of 
Not over 600 Volts, Nomina!. 

(A) Above Roofs. Overhead spans of open conductors and 
open multiconductor cables shall have a vertical clearance 
of not less than 2.5 m (8 ft) above the roof surface. The 
vertical clearance above the roof level shall be maintained 
for a distance not less than 900 mm (3 ft) in all directions 
from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from, the roof surface in accordance with the clear- 
ance requirements of 225.18. 

Exception No. 2: Where the voltage between conductors 
does not exceed 300, and the roof has a slope of 100 mm in 
300 mm (4 in. in 12 in.) or greater, a reduction in clearance 
to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (I) not more than 1.8 m (6 ft) 
of the conductors, 1.2 m (4 ft) horizontally, pass above the 
roof overhang and (2) they are terminated at a through-the- 
roof raceway or approved support. 

Exception No. 4: The requirement for maintaining the ver- 
tical clearance 900 mm (3 ft) from the edge of the roof shall 
not apply to the final conductor span where the conductors 
are attached to the side of a building. 

(B) From Nonbuilding or Nonbridge Structures. From 
signs, chimneys, radio and television antennas, tanks, and 
other nonbuilding or nonbridge structures, clearances — 
vertical, diagonal, and horizontal — shall not be less than 
900 mm (3 ft). 

(C) Horizontal Clearances. Clearances shall not be less 
than 900 mm (3 ft). 

(D) Final Spans. Final spans of feeders or branch circuits 
shall comply with 225.19(D)(1), (D)(2), and (D)(3). 

(1) Clearance from Windows. Final spans to the building 
they supply, or from which they are fed, shall be permitted 
to be attached to the building, but they shall be kept not less 
than 900 mm (3 ft) from windows that are designed to be 
opened, and from doors, porches, balconies, ladders, stairs, 
fire escapes, or similar locations. 



Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3 -ft) 
requirement. 

(2) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they 
might be reached shall be maintained in accordance with 
225.18. 

(3) Building Openings. The overhead branch-circuit and 
feeder conductors shall not be installed beneath openings 
through which materials may be moved, such as openings 
in farm and commercial buildings, and shall not be installed 
where they obstruct entrance to these buildings' openings. 

(E) Zone for Fire Ladders. Where buildings exceed three 
stories or 15 m (50 ft) in height, overhead lines shall be 
arranged, where practicable, so that a clear space (or zone) at 
least 1.8 m (6 ft) wide will be left either adjacent to the build- 
ings or beginning not over 2.5 m (8 ft) from them to facilitate 
the raising of ladders when necessary for fire fighting. 

225.20 Mechanical Protection of Conductors. Mechani- 
cal protection of conductors on buildings, structures, or 
poles shall be as provided for services in 230.50. 

225.21 Multiconductor Cables on Exterior Surfaces of 
Buildings. Supports for multiconductor cables on exterior 
surfaces of buildings shall be as provided in 230.51. 

225.22 Raceways on Exterior Surfaces of Buildings or 
Other Structures. Raceways on exteriors of buildings or 
other structures shall be arranged to drain and shall be 
suitable for use in wet locations. 

225.24 Outdoor Lampholders. Where outdoor lamphold- 
ers are attached as pendants, the connections to the circuit 
wires shall be staggered. Where such lampholders have 
terminals of a type that puncture the insulation and make 
contact with the conductors, they shall be attached only to 
conductors of the stranded type. 

225.25 Location of Outdoor Lamps. Locations of lamps 
for outdoor lighting shall be below all energized conduc- 
tors, transformers, or other electric utilization equipment, 
unless either of the following apply: 

( 1 ) Clearances or other safeguards are provided for relamping 
operations. 

(2) Equipment is controlled by a disconnecting means that 
can be locked in the open position. 

225.26 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead conductor spans. 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-73 



225.27 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.27 Raceway Seal. Where a raceway enters a building 
or structure from an underground distribution system, it 
shall be sealed m accordance with 300 5(G) Spare or un- 
used racew tys hall ihu be seale '. Sealai ts -.nil! be i-Jbn 
tified for use with the cable insulation', shield or other 
< omponents. 

II. Buildings or Other Structures Supplied by a 
Feeder(s) or Branch Circuit(s) 

225.30 Number of Supplies. A building or other structure 
that is served by a branch circuit or feeder on the load side 
of a service disconnecting means shall be supplied by only 
one feeder or branch circuit unless permitted in 225.30(A) 
through (E). For the purpose of this section a rnultiwire 
hi an. Si cir< uii shall be considered \ single circuit, 

Wheie ? branch circuit oi feedei originates in these 
additional buildups oi othei structun % only o k feedei o; 
branch circuit shall be permitted to supply powei back to 
the original building oi structure unless permitted in 
225.30(A) through (E). 

For the purpose of this section, a rnultiwire branch cir- 
cuit shall be considered a single circuit. 

(A) Special Conditions. Additional feeders or branch cir- 
cuits shall be permitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 

(6) Systems designed for connection to multiple sources of 
supply for the purpose of enhanced reliability 

(B) Special Occupancies. By special permission, addi- 
tional feeders or branch circuits shall be permitted for ei- 
ther of the following: 

(1) Multiple-occupancy buildings where there is no space 
available for supply equipment accessible to all occupants 

(2) A single building or other structure sufficiently large to 
make two or more supplies necessary 

(C) Capacity Requirements. Additional feeders or branch 
circuits shall be permitted where the capacity requirements are 
in excess of 2000 amperes at a supply voltage of 600 volts or 
less. 

(D) Different Characteristics. Additional feeders or branch 
circuits shall be permitted for different voltages, frequen- 
cies, or phases or for different uses, such as control of 
outside lighting from multiple locations. 

(E) Documented Switching Procedures. Additional feed- 
ers or branch circuits shall be permitted to supply installa- 



tions under single management where documented safe 
switching procedures are established and maintained for 
disconnection. 

225.31 Disconnecting Means. Means shall be provided 
for disconnecting all ungrounded conductors that supply or 
pass through the building or structure. 

225.32 Location. The disconnecting means shall be in- 
stalled either inside or outside of the building or structure 
served or where the conductors pass through the building or 
structure. The disconnecting means shall be at a readily 
accessible location nearest the point of entrance of the con- 
ductors. For the purposes of this section, the requirements 
in 230.6 shall be utilized. 

Exception No. 1: For installations under single manage- 
ment, where documented safe switching procedures are es- 
tablished and maintained for disconnection, and where the 
installation is monitored by qualified individuals, the dis- 
connecting means shall be permitted to be located else- 
where on the premises. 

Exception No. 2: For buildings or other structures quali- 
fying under the provisions of Article 685, the disconnecting 
means shall be permitted to be located elsewhere on the 
premises. 

Exception No. 3: For towers or poles used as lighting 
standards, the disconnecting means shall be permitted to be 
located elsewhere on the premises. 

Exception No. 4: For poles or similar structures used, only 
for support of signs installed in accordance with Article 
600, the disconnecting means shall be permitted to be lo- 
cated elsewhere on the premises. 

225.33 Maximum Number of Disconnects. 

(A) General. The disconnecting means for each supply 
permitted by 225.30 shall consist of not more than six 
switches or six circuit breakers mounted in a single enclo- 
sure, in a group of separate enclosures, or in or on a switch- 
board. There shall be no more than six disconnects per 
supply grouped in any one location. 

Exception: For the purposes of this section, disconnecting 
means used solely for the control circuit of the ground-fault 
protection system, or the control circuit of the power- 
operated supply disconnecting means, installed as part of 
the listed equipment, shall not be considered a supply dis- 
connecting means. 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers capable of individual operation shall be permit- 
ted on rnultiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 
equipped with identified handle ties or a master handle to 



70-74 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.39 



disconnect all ungrounded conductors with no more than 
six operations of the hand. 

225.34 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
225.33 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six disconnecting means 
permitted in 225.33, where used only for a water pump also 
intended to provide fire protection, shall be permitted to be 
located remote from the other disconnecting means. 

(B) Additional Disconnecting Means. The one or more 
additional disconnecting means for fire pumps or for emer- 
gency, legally required standby or optional standby system 
permitted by 225.30 shall be installed sufficiently remote 
from the one to six disconnecting means for normal supply 
to minimize the possibility of simultaneous interruption of 
supply. 

225.35 Access to Occupants. In a multiple-occupancy 
building, each occupant shall have access to the occupant's 
supply disconnecting means. 

Exception: In a multiple-occupancy building where elec- 
tric supply and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the supply discon- 
necting means supplying more than one occupancy shall be 
permitted to be accessible to authorized management per- 
sonnel only. 

225.36 Suitable for Service Equipment. The disconnect- 
ing means specified in 225.31 shall be suitable for use as 
service equipment. 

Exception: For garages and outbuildings on residential 
property, a snap switch or a set of 3-way or 4-way snap 
switches shall be permitted as the disconnecting means. 

225.37 Identification. Where a building or structure has any 
combination of feeders, branch circuits, or services passing 
through it or supplying it, a permanent plaque or directory 
shall be installed at each feeder and branch-circuit disconnect 
location denoting all other services, feeders, or branch circuits 
supplying that building or structure or passing through that 
building or structure and the area served by each. 

Exception No. 1: A plaque or directory shall not be re- 
quired for large-capacity multibuilding industrial installa- 
tions under single management, where it is ensured that 
disconnection can be accomplished by establishing and 
maintaining safe switching procedures. 

Exception No. 2: This identification shall not be required 
for branch circuits installed from a dwelling unit to a sec- 
ond building or structure. 



225.38 Disconnect Construction. Disconnecting means 
shall meet the requirements of 225.38(A) through (D). 

Exception: For garages and outbuildings on residential 
property, snap switches or 3-way or 4-way snap switches shall 
be permitted as the disconnecting means. 

(A) Manually or Power Operable. The disconnecting 
means shall consist of either (1) a manually operable switch or 
a circuit breaker equipped with a handle or other suitable op- 
erating means or (2) a power-operable switch or circuit 
breaker, provided the switch or circuit breaker can be opened 
by hand in the event of a power failure. 

(B) Simultaneous Opening of Poles. Each building or struc- 
ture disconnecting means shall simultaneously disconnect all 
ungrounded supply conductors that it controls from the build- 
ing or structure wiring system. 

(C) Disconnection of Grounded Conductor. Where the 
building or structure disconnecting means does not discon- 
nect the grounded conductor from the grounded conductors 
in the building or structure wiring, other means shall be 
provided for this purpose at the location of disconnecting 
means. A terminal or bus to which all grounded conductors 
can be attached by means of pressure connectors shall be 
permitted for this purpose. 

In a multisection switchboard, disconnects for the 
grounded conductor shall be permitted to be in any sec- 
tion of the switchboard, provided any such switchboard 
section is marked. 

(D) Indicating. The building or structure disconnecting 
means shall plainly indicate whether it is in the open or 
closed position. 

225.39 Rating of Disconnect. The feeder or branch-circuit 
disconnecting means shall have a rating of not less than the 
calculated load to be supplied, determined in accordance 
with Parts I and II of Article 220 for branch circuits, Part III 
or IV of Article 220 for feeders, or Part V of Article 220 for 
farm loads. Where the branch circuit or feeder disconnect- 
ing means consists of more than one switch or circuit 
breaker, as permitted by 225.33, combining the ratings of 
all the switches or circuit breakers for determining the rat- 
ing of the disconnecting means shall be permitted. In no 
case shall the rating be lower than specified in 225.39(A), 
(B), (C), or (D). 

(A) One-Circuit Installation. For installations to supply 
only limited loads of a single branch circuit, the branch 
circuit disconnecting means shall have a rating of not less 
than 15 amperes. 

(B) Two-Circuit Installations. For installations consisting 
of not more than two 2-wire branch circuits, the feeder or 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-75 



225.40 



ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



branch-circuit disconnecting means shall have a rating of 
not less than 30 amperes. 

(C) One-Family Dwelling. For a one-family dwelling, the 
feeder disconnecting means shall have a rating of not less 
than 100 amperes, 3-wire. 

(D) All Others. For all other installations, the feeder or 
branch-circuit disconnecting means shall have a rating of 
not less than 60 amperes. 

225.40 Access to Overcurrent Protective Devices. Where 
a feeder overcurrent device is not readily accessible, branch- 
circuit overcurrent devices shall be installed on the load side, 
shall be mounted in a readily accessible location, and shall be 
of a lower ampere rating than the feeder overcurrent device. 

III. Over 600 Volts 

225.50 Sizing of Conductors. The sizing of conductors 
over 600 volts shall be in accordance with 210.19(B) for 
branch circuits and 215.2(B) for feeders. 

225.51 Isolating Switches. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute a 
building disconnecting means, an isolating switch with visible 
break contacts and meeting the requirements of 230.204(B), 
(C), and (D) shall be installed on the supply side of the dis- 
connecting means and all associated equipment. 

Exception: The isolating switch shall not be required where 
the disconnecting means is mounted on removable truck pan- 
els or metal-enclosed switchgear units that cannot be opened 
unless the circuit is disconnected and that, when removed from 
the normal operating position, automatically disconnect the 
circuit breaker or switch from all energized parts. 

225.52 Disconnecting Means. 

(A) Location. A building or structure disconnecting means 
shall be located in accordance with 225.32, or it shall be 
electrically operated by a similarly located remote-control 
device. 

(B) Type. Each building or structure disconnect shall si- 
multaneously disconnect all ungrounded supply conductors 
it controls and shall have a fault-closing rating not less than 
the maximum available short-circuit current available at its 
supply terminals. 

Exception: Where the m.,:iit l,, nl disconnecting means 
consists of fused cutouts the simult meous disconnection oj 
all ungrounded supply conductors shall not be required if 
there is a means to dis -onnect tin load before ope",},}' the 
cutouts. A permanent legible sign Aal' be installed tdja- 
cent to the fused cutouts indicating the above requ rement. 



Where fused switches or separately mounted fuses are in- 
stalled, the fuse characteristics shall be permitted to contribute 
to the fault closing rating of the disconnecting means. 

(C) Locking. Di-,cf.'!'iec!iag nicj't; siwi! be capable of be- 
ing loci*. 1 !■! the open position. The pptvH'.cn- foi locking 
shall regain in place \, nit di without the lock iiHi-illed. 

Exception: Where an individual disci meeting means con- 
sists 'of fiti d cutouts a suitable en I sure capable of being 
Uh ked and sized to ■ ontain all < utoutfusi nohlers ihall be 
installed at a convenient hi ation so the fused cutouts. 

(D) Indicating Disconn cting i leans shall clearly indicate 
whether iV^ are in the open "off' oi closed "on" position. 

(E) Uniform Kx-iitHWu. Where disconnecting means handles 
are operated 'eiin..«lh. rt>>. "up" p >sition oi (he hmtdic -.hi"!! be 
the "on" position. 

Exception: A sw tching device having more than o >e "on" 
position, such as a double throw switch, shall not be re 
quired to comply with this requirement. 

(F) Idc-SiUfiifif 'u.j. Where a hu'KVig or suucfuie has any 
« •jiTibi.ijJu n <-f i \ d';s bi iiicu urtt'M oi services passini 
through oi supplying it, a permanent plaque or a'ce"ln ( \ 
>Jiiill be insi .il.M at eac'i feedei and branch tircii! disconnect 
location ih . denote .- ii! '/i'^'i services. feeders, or branch eu 
cuits .supplying that building or .structure or passing through 
that buildinp or -kih )<«>.. and me irea served i>y each. 

225.5(» Inspections and Tests. 

(A) Prc-Energization ind l *> .;:.!< « rests. '■'■ - com- 
plete Jeclrieal system shall be t.CiU-iui,.iic: tested r.hcn 
first installed on-site. Each protective switching, and con- 
trol circt 1 '! r.hoi) be adjusted in accordance with she recdm- 
ineniJiitions ui the protective device stud) and tested b> 
.tula! operation usui- current injection <r equi ".Irni '"dh- 
otis a i necessary to ensure thai each and every such circuij 
operate:- correctly to the satisfaction of the jrthoiity having 
jurisdiction. 

(1) Instrument Transformers. All instrument u inslbrm 

ers ,h. i 1 h te ted <\. ve >l a\i, ;i pola it ' .yi burden. 

(2) Protective Relays. Each protective relay shall be dem- 
onstrated to operate by injecting current di voltage, or both. 
at the associated instrument transformer output terminal 
and observing ttmt the associated switching and signaling 
fiwc.it.ii-. occur corrcctiy and ii» pi'jpc i>si<e and sequence 
to accou'if ii.-fi the protective function intended. 

(3) Swiic'J'.;; Circuits liach switch ng cuc'iu shall be ob- 
served to operate the a'sscw iated equipment hcu>y switched 

(4) Control audi .Sijra&l Llicnits. Each control or signal 
circuit shall be observed to perform its proper control func- 
tion ()] j.T'idllCv. .) Xin'CC! MJ-'iMl lULpHF 



70-76 



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ARTICLE 225 — OUTSIDE BRANCH CIRCUITS AND FEEDERS 



225.76 



(5) Meientaa fjsv nits. a1J m ".'fir' ; t ircuit Jnll he veri- 
fy,! to operate correctly fio..i voltage jo*, tumm sources, 
sirnil iriy to protective relay circuits. 

(6) Accept; see Tests. Conipli le acet ptyiu ; tests -.hall be 
performed -"'la th< station installation is coi "loted, on ;M 
.i-i.i'ihiit >, equipment, c< nductors .unl Dontn 1 and protei 
tive system-, as applicable, to verify the integrity of all the 

■ ems. 

(7) Relays and Metering Utilizing Phase Differences. All 

n lay: 'no men iu;> ma us. \ '"*«•■ cliff* ret . e n i <>pi ! it on 
"•h.ill f )'" verified by measuring phase angles at iln. relay 
undei <.r!«nt load conditions afb i oj\.i*iri<i i-otiU"jeu:c 

(B) Tesl Report. A test report covering the results of I he- 
tests required ni 225 56(A) shall \» delivered to the authoi 
it] having jurisdiction prioi to mergizaMon. 

Informational Note: For acceptance specifications, see 
;<yi~\ ATS-2007 Aecepianci testing $p '• ificatiom fat 
Electrical Powei Distribution Equipment and Systems 
published b> .he InterNatioiial Electrical Testing 
Association^ 

225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land. 

(A) 22 kV, Nominal, to Ground or Less. The clearances 
over roadways, walkways, rail, water, and open land for con- 
ductors and live parts up to 22 kV, nominal, to ground or less 
shall be not less than the values shown in Table 225.60. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.60 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

(C) Special Cases. For special cases, such as where cross- 
ings will be made over lakes, rivers, or areas using large 
vehicles such as mining operations, specific designs shall 
be engineered considering the special circumstances and 
shall be approved by the authority having jurisdiction. 

Informational Note: For additional information, see ANSI 
C2-2007, National Electrical Safety Code. 

225.61 Clearances over Buildings and Other Structures. 

(A) 22 kV Nominal to Ground or Less. The clearances 
over buildings and other structures for conductors and live 
parts up to 22 kV, nominal, to ground or less shall be not 
less than the values shown in Table 225.61. 

(B) Over 22 kV Nominal to Ground. Clearances for the 
categories shown in Table 225.61 shall be increased by 
10 mm (0.4 in.) per kV above 22,000 volts. 

Informational Note: For additional information, see ANSI 
C2-2007, National Electrical Safety Code. 



Table 225.60 Clearances over Roadways, Walkways, Rail, 
Water, and Open Land 



Clearance 


Location 


m 


ft 


Open land subject to vehicles, 


5.6 


18.5 


cultivation, or grazing 






Roadways, driveways, parking 


5.6 


18.5 


lots, and alleys 






Walkways 


4.1 


13.5 


Rails 


8.1 


26.5 


Spaces and ways for pedestrians 


4.4 


14.5 


and restricted traffic 






Water areas not suitable for 


5.2 


17.0 


boating 







Table 225.61 Clearances over Buildings and Other 
Structures 



Clearance from 

Conductors or Live 

Parts from: 



Horizontal 



Vertical 



m ft 



Building walls, 

projections, and 

windows 
Balconies, catwalks, and 

similar areas accessible 

to people 
Over or under roofs or 

projections not readily 

accessible to people 
Over roofs accessible to 

vehicles but not trucks 
Over roofs accessible to 

trucks 
Other structures 



2.3 7.5 



2.3 7.5 



4.1 

3.8 

4.1 
5.6 



13.5 

12.5 

13.5 
18.5 



2.3 7.5 



225.70 Substations. 
(A) Warning Signs. 

(1) General. A [>?>■> n ient, legible \\ truing m ii< e „ : rrj ing; 
the wording "DANGI-R HIGH VOITAGF" shall be 

placed in a conspicuous position in the tol lowing areas: 

(a) At all entrances i - electrical e'|i>iomeu> mlts and 
electrical eijuipiuei" i >oj is, areas, r -t enelo ures 

(b) At points of access to conductors on all high- 
voltage conduit systems and cabh systems 

(c) On aii ■ ablt tray; containing high voltage conduc 
tors with the maximum spacing vi warning notices not to 
exceed 3 m (10 ft.) 

(2) Isolating Equipment. Permanent legible signs shall be 
installed it isolating .qu'pni-"^ w ' ning tgatrist operation 
wU<>> > < rying current 'ink" the equipment t- ineilofVo 
so that ;>. cannot be operated under load. 



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NATIONAL ELECTRICAL CODE 



70-77 



230.1 



ARTICLE 230 — SERVICES 



(3) Fuse Locations. Suitable warning signs siiall be 
elected in a . . s icuoi la< a . to fuses 'ami •. 
operators nc to itiibi - fuses while tlie circuit i< energized. 

(4) Backfeed. The following steps shall be taken where the 
possibility of bad feed exists: 

(a) Eacii ftoap op.tuied isolating switch or disconnect 
in.' in- hi shall i .u i »' .)'inii/i notice i<> i"u effect that 
contacts on either side of the device might be energized. 

(b) A permanent legible, single _i<k diagram ol the 
station switching arrangement, < leail-' identifying eacl 
,»uit t ui connection v> itv lu;Ji-v«l:>gt section shall be 
,)iOi"i1.v) hi a conspicuous location 'vit'i-u sight of each 
point of connection. 

(5) Mt al-K.nclosed and Metal-Clad Switchgear. Win r< 

m t'.| ni. 'ii ed witehgt h i in tailed n folli w ng steps 
shall be taken: 

(a) "- permanent, legible ingle-lim diagram of the 
kvlijia, '.!<-<! I be p >.idtd in i readily visible f,"Hv.n 

within sight of the switchgear. and die. diagram shall 
clearly identify 'ittr-'-IovK isolation m^ans wl all po.iHf 
-mum. - oi ^oluiie n ti't. in'idM-iiiM! uid>" r.-miji (w emei 
gene; t onriitioi]' , n.'inlw aJl r'qnir.'iieni : u 'twi^d ir 
each cubicle, and the marking oi. (lie switchgear shall 
cross-reference the diagram. 

Exception to (a) When the equipment consists solely >f a 
ingle cubicle or meta enclosed i 'it tbstation containing 
only one net of high voltage switching devices, diagrams 
shall tot he n q'-ired 

(b) Permanent, legible signs shall be installed on panels 
or doors '.in' provide access to live parts Over 600 volts and 
shall carry the wording "DANGER HIGH VOLTAGE" 

to warn of th< danger oi opi ninj "hik energized. 

(c) Where the panel provides access to parts that can 
onl) be de-energized and visibly rolate-J by the serving 
utility, the warning shall include that access is Hit ited to the 
serving utility oi following an anilioii'anon of the serving 
utility. 



ARTICLE 23ft 
Services 



230.1 Scope. This article covers service conductors and 
equipment for control and protection of services and their 
installation requirements. 

Informational Note: See Figure 230.1. 



General Part I 

Overhead Service Conductors Part II 

Underground Service Conductors Part III 

Service-Entrance Conductors Part IV 

Service Equipment — General Part V 

Service Equipment — Disconnecting Means Part VI 

Service Equipment — Overcurrent Protection Part VII 

Services Exceeding 600 Volts, Nominal Part VIII 



Source 



Part II 



230.24 



Overhead 
Last pole 

Overhead 
service conductors 
Clearances 



Service head 



Underground 
Street main 



Underground Part I 

service conductors 



Service-entrance 
conductors 



Service equipment — general 
Grounding and bonding 

Disconnecting means 



Depth of burial 
and protection 



Terminal box, 
meter, or other 
enclosure 



230.49 



Part IV 



PartV 
Article 250 

Part VI 



Overcurrent protection 




Part VII 










Branch circuits 
Feeders 


Articles 210, 225 
Articles 215, 225 











Figure 230.1 Services. 

I. General 

230.2 Number of Services. A building or other structure 
served shall be supplied by only one service unless permit- 
ted in 230.2(A) through (D). For the purpose of 230.40, 
Exception No. 2 only, underground sets of conductors, 
1/0 AWG and larger, running to the same location and con- 
nected together at their supply end but not connected to- 
gether at their load end shall be considered to be supplying 
one service. 

(A) Special Conditions. Additional services shall be per- 
mitted to supply the following: 

(1) Fire pumps 

(2) Emergency systems 

(3) Legally required standby systems 

(4) Optional standby systems 

(5) Parallel power production systems 

(6) Systems designed for connection to multiple sources of 
supply for the purpose of enhanced reliability 



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NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 230 — SERVICES 



230.23 



(B) Special Occupancies. By special permission, additional 
services shall be permitted for either of the following: 

(1) Multiple-occupancy buildings where there is no available 
space for service equipment accessible to all occupants 

(2) A single building or other structure sufficiently large to 
make two or more services necessary 

(C) Capacity Requirements. Additional services shall be 
permitted under any of the following: 

(1) Where the capacity requirements are in excess of 2000 
amperes at a supply voltage of 600 volts or less 

(2) Where the load requirements of a single-phase installa- 
tion are greater than the serving agency normally sup- 
plies through one service 

(3) By special permission 

(D) Different Characteristics. Additional services shall 
be permitted for different voltages, frequencies, or phases, 
or for different uses, such as for different rate schedules. 

(E) Identification. Where a building or structure is sup- 
plied by more than one service, or any combination of 
branch circuits, feeders, and services, a permanent plaque 
or directory shall be installed at each service disconnect 
location denoting all other services, feeders, and branch 
circuits supplying that building or structure and the area 
served by each. See 225.37. 

230.3 One Building or Other Structure Not to Be Sup- 
plied Through Another. Service conductors supplying a 
building or other structure shall not pass through the inte- 
rior of another building or other structure. 

230.6 Conductors Considered Outside the Building. 

Conductors shall be considered outside of a building or 
other structure under any of the following conditions: 

(1) Where installed under not less than 50 mm (2 in.) of 
concrete beneath a building or other structure 

(2) Where installed within a building or other structure in a 
raceway that is encased in concrete or brick not less 
than 50 mm (2 in.) thick 

(3) Where installed in any vault that meets the construction 
requirements of Article 450, Part III 

(4) Where installed in conduit and under not less than 
450 mm (18 in.) of earth beneath a building or other 
structure 

(5) Where ; r>M'illed in overt* ad service mas! ■ m the out 
side surface of thi building traveling thfoyjgb the eave 
of that building to niece the requirements of 230.24 

230.7 Other Conductors in Raceway or Cable. Conduc- 
tors other than service conductors shall not be installed in 
the same service raceway or service cable. 



Exception No. 1: Grounding conductors and bonding 
jumpers. 

Exception No. 2: Load management control conductors 
having overcurrent protection. 

230.8 Raceway Seal. Where a service raceway enters a 
building or structure from an underground distribution sys- 
tem, it shall be sealed in accordance with 300.5(G). Spare 
or unused raceways shall also be sealed. Sealants shall be 
identified for use with the cable insulation, shield, or other 
components. 

230.9 Clearances on Buildings. Service conductors and 
final spans shall comply with 230.9(A), (B), and (C). 

(A) Clearances. Service conductors installed as open con- 
ductors or multiconductor cable without an overall outer 
jacket shall have a clearance of not less than 900 mm (3 ft) 
from windows that are designed to be opened, doors, 
porches, balconies, ladders, stairs, fire escapes, or similar 
locations. 

Exception: Conductors run above the top level of a win- 
dow shall be permitted to be less than the 900-mm (3 -ft) 
requirement. 

(B) Vertical Clearance. The vertical clearance of final 
spans above, or within 900 mm (3 ft) measured horizontally 
of, platforms, projections, or surfaces from which they 
might be reached shall be maintained in accordance with 
230.24(B). 

(C) Building Openings. Overhead service conductors 
shall not be installed beneath openings through which ma- 
terials may be moved, such as openings in farm and com- 
mercial buildings, and shall not be installed where they 
obstruct entrance to these building openings. 

230.10 Vegetation as Support. Vegetation such as trees 
shall not be used for support of overhead service conductors. 

II. Overhead Service Conductors 

230.22 Insulation or Covering. Individual conductors 
shall be insulated or covered. 

Exception: The grounded conductor of a multiconductor 
cable shall be permitted to be bare. 

230.23 Size and Rating. 

(A) General. Conductors shall have sufficient ampacity to 
carry the current for the load as calculated in accordance 
with Article 220 and shall have adequate mechanical 

strength. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-79 



230.24 



ARTICLE 230— SERVICES 



(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG hard-drawn copper or equivalent. 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size as required by 
250.24(C). 

230.24 Clearances. Overhead service conductors shall not 
be readily accessible and shall comply with 230.24(A) 
through (E) for services not over 600 volts, nominal. 

(A) Above Roofs. Conductors shall have a vertical clear- 
ance of not less than 2.5 m (8 ft) above the roof surface. 
The vertical clearance above the roof level shall be main- 
tained for a distance of not less than 900 mm (3 ft) in all 
directions from the edge of the roof. 

Exception No. 1: The area above a roof surface subject to 
pedestrian or vehicular traffic shall have a vertical clear- 
ance from the roof surface in accordance with the clear- 
ance requirements of 230.24(B). 

Exception No. 2: Where the voltage between conductors 
does not exceed 300 and the roof has a slope of 100 mm in 
300 mm (4 in. in 12 in.) or greater, a reduction in clearance 
to 900 mm (3 ft) shall be permitted. 

Exception No. 3: Where the voltage between conductors 
does not exceed 300, a reduction in clearance above only 
the overhanging portion of the roof to not less than 450 mm 
(18 in.) shall be permitted if (1) not more than 1.8 m (6 ft) 
of overhead service conductors, 1.2 m (4 ft) horizontally, 
pass above the roof overhang, and (2) they are terminated 
at a through-the-roof raceway or approved support. 

Informational Note: See 230.28 for mast supports. 

Exception No. 4: The requirement for maintaining the ver- 
tical clearance 900 mm (3 ft) from the edge of the roof shall 
not apply to the final conductor span where the service 
drop is attached to the side of a building. 

Exception No. 5: Where the voltage between conductors 
does not exceed 300 and the rooj area is guarded or iso- 
lated, a reduction in < learance to 900 mm (3 ft) shall be 
permitted 

(B) Vertical Clearance for Overhead Service Conduc- 
tors. Overhead service conductors, where not in excess of 
600 volts, nominal, shall have the following minimum 
clearance from final grade: 

(1) 3.0 m (10 ft) — at the electrical service entrance to 
buildings, also at the lowest point of the drip loop of 



the building electrical entrance, and above areas or 
sidewalks accessible only to pedestrians, measured 
from final grade or other accessible surface only for 
service-drop cables supported on and cabled together 
with a grounded bare messenger where the voltage 
does not exceed 1 50 volts to ground 

(2) 3.7 m (12 ft) — over residential property and drive- 
ways, and those commercial areas not subject to truck 
traffic where the voltage does not exceed 300 volts to 
ground 

(3) 4.5 m (15 ft) — for those areas listed in the 3.7-m (12-ft) 
classification where the voltage exceeds 300 volts to 
ground 

(4) 5.5 m (18 ft) — over public streets, alleys, roads, park- 
ing areas subject to truck traffic, driveways on other 
than residential property, and other land such as culti- 
vated, grazing, forest, and orchard 

(C) Clearance from Building Openings. See 230.9. 

(D) Clearance from Swimming Pools. See 680.8. 

(E) Clearance from Communication Wires and Cables. 

U< irance from comtnunication wires ai d < able;- -lull be in 
accordance with Sll(').44( A)(4). 

230.26 Point of Attachment. The point of attachment of 
the service-drop conductors to a building or other structure 
shall provide the minimum clearances as specified in 230.9 
and 230.24. In no case shall this point of attachment be less 
than 3.0 m (10 ft) above finished grade. 

230.27 Means of Attachment. Multiconductor cables used 
for overhe «i service conductors shall be attached to build- 
ings or other structures by fittings identified for use with 
service conductors. Open conductors shall be attached to 
fittings identified for use with service conductors or to non- 
combustible, nonabsorbent insulators securely attached to 
the building or other structure. 

230.28 Service Masts as Supports. Where a service mast 
is used for the support of service-drop conductors, it shall 
be of adequate strength or be supported by braces or guys 
to withstand safely the strain imposed by the service drop. 
Where raceway-type service masts are used, all raceway 
fittings shall be identified for use with service masts. Only 
power service-drop conductors shall be permitted to be at- 
tached to a service mast. 

230.29 Supports over Buildings. Service conductors 
passing over a roof shall be securely supported by substan- 
tial structures. Where practicable, such supports shall be 
independent of the building. 



70-80 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 230 — SERVICES 



230.41 



III. Underground Service Conductors 

230.30 Insulation. Service-lateral conductors shall be in- 
sulated for the applied voltage. 

Exception: A grounded conductor shall be permitted to be 
uninsulated, as follows: 

(1) Bare copper used in a raceway. 

(2) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 

(3) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 

(4) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
identified for underground use in a raceway or for di- 
rect burial. 

230.31 Size and Rating. 

(A) General. Underground service conductors shall have 
sufficient ampacity to carry the current for the load as cal- 
culated in accordance with Article 220 and shall have ad- 
equate mechanical strength. 

(B) Minimum Size. The conductors shall not be smaller 
than 8 AWG copper or 6 AWG aluminum or copper-clad 
aluminum. 

Exception: Conductors supplying only limited loads of a 
single branch circuit — such as small polyphase power, 
controlled water heaters, and similar loads — shall not be 
smaller than 12 AWG copper or 10 AWG aluminum or 
copper-clad aluminum. 

(C) Grounded Conductors. The grounded conductor shall 
not be less than the minimum size required by 250.24(C). 

230.32 Protection Against Damage. Underground service 
conductors shall be protected against damage in accordance 
with 300.5. Service conductors entering a building or other 
structure shall be installed in accordance with 230.6 or pro- 
tected by a raceway wiring method identified in 230.43. 

230.33 Spliced Conductors. Service conductors shall be 
permitted to be spliced or tapped in accordance with 
110.14, 300.5(E), 300.13, and 300.15. 

IV. Service-Entrance Conductors 

230.40 Number of Service-Entrance Conductor Sets. 

Each service drop, set of overhead sen ice conductors s- i 
of under. 1 1 ni' i u! ervice conductors or service lateral shall 
supply only one set of service-entrance conductors. 



Exception No. 1: A building with more than one occu- 
pancy shall be permitted to have one set of service- 
entrance conductors for each service, as defined in 230.2, 
run to each occupancy or group of occupancies. If the 
mmtl'"] of soviet disconnect locations foi any given clas- 
sification ■ >fsi i !"/. e di >es not exec ed six, i he n quit 'ments of 
230.2(E) shall apply at '•(■tit location if the number of 
service disconnect locations exceeds six for any given sup- 
ply classification ill service lisconn ct locations for all 
supph characteristic , togethet with n\ branch circuit or 
feeder supply idurces if applicable shall he clearly de- 
scribed using mutable graphics or text o> both on one or 
more plaques located in on approved readily ace, ssibk 
ioi ationis) on the building or structure st n ed and as near 
a . t'l'U tii able so tl > pointf s I oj . h > hmem ci , nti \ lies) for 
each service d>;>r oi \ervicc 'ate ml and fm each set of 
overhead or mulei utid se via < « nductors 

Exception No. 2: Where two to six service disconnecting 
means in separate enclosures are grouped at one location 
and supply separate loads from one service drop, set of 
overhead service conductors, set of underground service 
< cmdiH tors or service lateral, one set of service-entrance 
conductors shall be permitted to supply each or several 
such service equipment enclosures. 

Exception No. 3: A single-family dwelling unit and its 
accessory structures shall be permitted to have one set of 
service-entrance conductors run to each from a single ser- 
vice drop, set of over} ead sen;/ < condm tors, set of wider- 
ground service conductors, or service lateral. 
Exception No. 4: Two-family dwellings, multifamily dwell- 
ings, and mu tiple occupant ) buildings shall be permitted 
to have one set of service-entrance conductors installed to 
supply the circuits covered in 210.25. 
Exception No. 5: One set of service-entrance conductors 
connected to the supply side of the normal service discon- 
necting means shall be permitted to supply each or several 
systems covered by 230.82(5) or 230.82(6). 

230.41 Insulation of Service-Entrance Conductors. 

Service-entrance conductors entering or on the exterior of 
buildings or other structures shall be insulated. 

Exception: A grounded conductor shall be permitted to be 
uninsulated as follows: 

(1) Bare copper used in a raceway or part of a service 
cable assembly. 

(2) Bare copper for direct burial where bare copper is 
judged to be suitable for the soil conditions. 

(3) Bare copper for direct burial without regard to soil 
conditions where part of a cable assembly identified for 
underground use. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-81 



230.42 



ARTICLE 230 — SERVICES 



(4) Aluminum or copper-clad aluminum without individual 
insulation or covering where part of a cable assembly 
or identified for underground use in a raceway, or for 
direct burial. 

(5) Bare conductors used in an auxiliary gutter. 

230.42 Minimum Size and Rating. 

(A) General. The ampacity of the service-entrance con- 
ductors before the application of any adjustment or correc- 
tion factors shall not be less than either 230.42(A)(1) or 
(A)(2). Loads shall be determined in accordance with Part 
III, IV, or V of Article 220, as applicable. Ampacity shall be 
determined from 310.15. The maximum allowable current 
of busways shall be that value for which the busway has 
been listed or labeled. 

(1) The sum of the noncontinuous loads plus 125 percent 
of continuous loads 

Exception: Grounded conductors that an nm connected to 
an overcurrent device shtd be permitted to be sized at 
WO percent of the continuous end noncontinuous load. 

(2) The sum of the noncontinuous load plus the continuous 
load if the service-entrance conductors terminate in an 
overcurrent device where both the overcurrent device 
and its assembly are listed for operation at 100 percent 
of their rating 

(B) Specific Installations. In addition to the requirements 
of 230.42(A), the minimum ampacity for ungrounded con- 
ductors for specific installations shall not be less than the 
rating of the service disconnecting means specified in 
230.79(A) through (D). 

(C) Grounded Conductors. The grounded conductor 
shall not be smaller than the minimum size as required 
by 250.24(C). 

230.43 Wiring Methods for 600 Volts, Nominal, or Less. 

Service-entrance conductors shall be installed in accor- 
dance with the applicable requirements of this Code cover- 
ing the type of wiring method used and shall be limited to 
the following methods: 

(1) Open wiring on insulators 

(2) Type IGS cable 

(3) Rigid metal conduit 

(4) Intermediate metal conduit 

(5) Electrical metallic tubing 

(6) Electrical nonmetallic tubing (ENT) 

(7) Service-entrance cables 

(8) Wireways 

(9) Busways 

(10) Auxiliary gutters 

(11) Rigid polyvinyl chloride conduit (PVC) 



(12) Cablebus 

(13) Type MC cable 

(14) Mineral-insulated, metal-sheathed cable 

(15) Flexible metal conduit not over 1.8 m (6 ft) long or 
liquidtight flexible metal conduit not over 1.8 m (6 ft) 
long between raceways, or between raceway and ser- 
vice equipment, with equipment bonding jumper 
routed with the flexible metal conduit or the liq- 
uidtight flexible metal conduit according to the provi- 
sions of 250.102(A), (B), (C), and (E) 

(16) Liquidtight flexible nonmetallic conduit 

(17) High iensitj polyethylene conduit (HOPE) 

(18) N()iinut:«Jin iiiiJci^Kiund conduil with conductors 
(NUCC) 

(19) Reinforced Ihermosetting r< •>!/. conduit (RTRC) 

230.44 Cable Trays. Cable tray systems shall be permitted 
to support service-entrance conductors. Cable trays used to 
support service-entrance conductors shall contain only 
service-entrance conductors and .lull be limited lo the fol- 
lowing methods: 

(1) Type SE cable 

(2) Type MC cable 

(3) Type Ml cable 

(4) Type IGS cable 

(5) Single thermoplastic-insulated conductors 1/0 and 
largei with CT rating 

Such cable trays shall b. uH,ltfi d *ai5;i p-pnaj^o'h, 
affixed labels v-uh (he wording "Service Entrance Conduc- 
tors." TK labels sh 'IS be located so as to be visible aftei 
installation 'md p1'«"c«i so that the service-entrance , oii.iuc- 
tors are ->M,' to b? read i I) iraced through the enliit 'oj.r/th 
of the cubic tray. 

Exception: Conductors, other than service-entrance con- 
ductors, shall be permitted to be installed in a cable tray 
with service-entrance conductors, provided a solid fixed 
barrier of a material compatible with the cable tray is 
installed to separate the service-entrance conductors from 
other conductors installed in the cable tray. 

230.46 Spliced Conductors. Service-entrance conductors 
shall be permitted to be spliced or tapped in accordance 
with 110.14, 300.5(E), 300.13, and 300.15. 

230.50 Protection Against Physical Damage. 

(A) Underground Service-Entrance Conductors. Under- 
ground service-entrance conductors shall be protected 
against physical damage in accordance with 300.5. 

(B) All Other Service-Entrance Conductors. All other 
service-entrance conductors, other than underground ser- 



70-82 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 230 — SERVICES 



230.54 



vice entrance conductors, shall be protected against physi- 
cal damage as specified in 230.50(B)(1) or (B)(2). 

(1) Service-Entrance Cables. Scrvice-c 'Mice cables, 
where subject to physical damage, shall be protected by any 
of the following: 

(1) Rigid metal conduit 

(2) Intermediate metal conduit 

(3) Schedule 80 PVC conduit 

(4) Electrical metallic tubing 

(5) Reinforced thermosetting resin conduit (RTRC) 

(6) Other approved means 

(2) Other Than S^rvice-EntrSnce Cables. Individual open 

conductors and cables, other than servie< -entrance cables, 
shall not be installed within 3.0 m (10 ft) of grade level or 
where exposed to physical damage. 

Exception: Type MI and Type MC cable shall be permitted 
within 3.0 m (10 ft) of grade level where not exposed to 
physical damage or where protected in accordance with 
300.5(D). 

230.51 Mounting Supports. Service-entrance rabies or 
individual open service -entrance conductors shall be sup- 
ported as specified in 230.51(A), (B), or (C). 

(A) Service-Entrance Cables. Service-entrance cables shall 
be supported by straps or other approved means within 
300 mm (12 in.) of every service head, gooseneck, or connec- 
tion to a raceway or enclosure and at intervals not exceeding 
750 mm (30 in.). 

(B) Other Cables. Cables that are not approved for mounting 
in contact with a building or other structure shall be mounted 
on insulating supports installed at intervals not exceeding 
4.5 m (15 ft) and in a manner that maintains a clearance of not 
less than 50 mm (2 in.) from the surface over which they pass. 

(C) Individual Open Conductors. Individual open con- 
ductors shall be installed in accordance with Table 230.51(C). 
Where exposed to the weather, the conductors shall be 
mounted on insulators or on insulating supports attached to 



racks, brackets, or other approved means. Where not exposed 
to the weather, the conductors shall be mounted on glass or 
porcelain knobs. 

230.52 Individual Conductors Entering Buildings or 
Other Structures. Where individual open conductors enter 
a building or other structure, they shall enter through roof 
bushings or through the wall in an upward slant through 
individual, noncombustible, nonabsorbent insulating tubes. 
Drip loops shall be formed on the conductors before they 
enter the tubes. 

230.53 Raceways to Drain. Where exposed to the weather, 
raceways enclosing service-entrance conductors shall be 
suitable for use in wet locations and arranged to drain. 
Where embedded in masonry, raceways shall be arranged 
to drain. 

230.54 Overhead Service Locations. 

(A) Service Head. Service raceways shall be equipped 
with a service head at the point of connection to service- 
drop or overhead service conductors. The service head shall 
he listed for use in wet Ivctio'V 

(B) Service-Entrance Cables Equipped with Service 
Head or Gooseneck. Service-entrance cables shall be 
equipped with a service head. The service head shall be 
listed for use in wet location's. 

Exception: Type SE cable shall be permitted to be formed 
in a gooseneck and taped with a self-sealing weather- 
resistant thermoplastic. 

(C) Service Heads and Goosenecks Above Service-Drop 
or Overhead Service Attachment. Service heads and 
goosenecks in service-entrance cables shall be located 
above the point of attachment of the service-drop or over- 
head service conductors to the building or other structure. 

Exception: Where it is impracticable to locate the service 
head or gooseneck above the point of attachment, the ser- 
vice head or gooseneck location shall be permitted not 
farther than 600 mm (24 in.) from the point of attachment. 



Table 230.51(C) Supports 





Maximum Distance Between 


Minimum Clearance 












Supports 


Between Conductors 


From Surface 


Maximum 








Volts 


m ft 


mm in. 


mm m. 


600 


2.7 9 


150 6 


50 2 


600 


4.5 15 


300 12 


50 2 


300 


1.4 41/2 


75 3 


50 2 


600* 


1.4* 4'/ 2 * 


65* 2 1 /.* 


25* 1* 



*Where not exposed to weather. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-83 



230.56 



ARTICLE 230 — SERVICES 



(D) Secured. Service-entrance cables shall be held se- 
curely in place. 

(E) Separately Bushed Openings. Service heads shall 
have conductors of different potential brought out through 
separately bushed openings. 

Exception: For jacketed multiconductor service entrance 
cable without splice. 

(F) Drip Loops. Drip loops shall be formed on individual 
conductors. To prevent the entrance of moisture, service- 
entrance conductors shall be connected to the service-drop 
or overhead service conductors either (1) below the level of 
the service head or (2) below the level of the termination of 
the service-entrance cable sheath. 

(G) Arranged That Water Will Not Enter Service Race- 
way or Equipment. Service-entrani e awl overhead service 
conductors shall be arranged so that water will not enter 
service raceway or equipment. 

230.56 Service Conductor with the Higher Voltage to 
Ground. On a 4-wire, delta-connected service where the 
midpoint of one phase winding is grounded, the service 
conductor having the higher phase voltage to ground shall 
be durably and permanently marked by an outer finish that 
is orange in color, or by other effective means, at each 
termination or junction point. 

V. Service Equipment — General 

230.62 Service Equipment — Enclosed or Guarded. En- 
ergized parts of service equipment shall be enclosed as speci- 
fied in 230.62(A) or guarded as specified in 230.62(B). 

(A) Enclosed. Energized parts shall be enclosed so that 
they will not be exposed to accidental contact or shall be 
guarded as in 230.62(B). 

(B) Guarded. Energized parts that are not enclosed shall 
be installed on a switchboard, panelboard, or control board 
and guarded in accordance with 110.18 and 110.27. Where 
energized parts are guarded as provided in 110.27(A)(1) 
and (A)(2), a means for locking or sealing doors providing 
access to energized parts shall be provided. 

230.66 Marking. Service equipment rated at 600 volts or 
less shall be marked to identify it as being suitable for use 
as service equipment. All service equipment shall he listed, 
Individual meter socket enclosures shall not be considered 
service equipment. 

VI. Service Equipment — Disconnecting Means 

230.70 General. Means shall be provided to disconnect all 
conductors in a building or other structure from the service- 
entrance conductors. 



(A) Location. The service disconnecting means shall be in- 
stalled in accordance with 230.70(A)(1), (A)(2), and (A)(3). 

(1) Readily Accessible Location. The service disconnect- 
ing means shall be installed at a readily accessible location 
either outside of a building or structure or inside nearest the 
point of entrance of the service conductors. 

(2) Bathrooms. Service disconnecting means shall not be 
installed in bathrooms. 

(3) Remote Control. Where a remote control device(s) is 
used to actuate the service disconnecting means, the service 
disconnecting means shall be located in accordance with 
230.70(A)(1). 

(B) Marking. Each service disconnect shall be permanently 
marked to identify it as a service disconnect. 

(C) Suitable for Use. Each service disconnecting means 
shall be suitable for the prevailing conditions. Service 
equipment installed in hazardous (classified) locations shall 
comply with the requirements of Articles 500 through 5 17. 

230.71 Maximum Number of Disconnects. 

(A) General. The service disconnecting means for each ser- 
vice permitted by 230.2, or for each set of service-entrance 
conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, 
shall consist of not more than six switches or sets of circuit 
breakers, or a combination of not more than six switches and 
sets of circuit breakers, mounted in a single enclosure, in a 
group of separate enclosures, or in or on a switchboard. There 
shall be not more than six sets of disconnects per sendee 
grouped in any one location. 

For the purpose of this section, disconnecting means 
installed as part of listed equipment and used solely for the 
following shall not be considered a service disconnecting 
means: 

(1) Power monitoring equipment 

(2) Surge-protective device(s) 

(3) Control circuit of the ground-fault protection system 

(4) Power-operable service disconnecting means 

(B) Single-Pole Units. Two or three single-pole switches 
or breakers, capable of individual operation, shall be per- 
mitted on multiwire circuits, one pole for each ungrounded 
conductor, as one multipole disconnect, provided they are 
equipped with identified handle ties or a master handle to 
disconnect all conductors of the service with no more than 
six operations of the hand. 

Informational Note: See 408.36, Exception No. 1 and Ex- 
ception No. 3, for service equipment in certain panelboards, 
and see 430.95 for service equipment in motor control 
centers. 



70-84 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 230 — SERVICES 



230.82 



230.72 Grouping of Disconnects. 

(A) General. The two to six disconnects as permitted in 
230.71 shall be grouped. Each disconnect shall be marked 
to indicate the load served. 

Exception: One of the two to six service disconnecting 
means permitted in 230. 71, where used only for a water 
pump also intended to provide fire protection, shall be per- 
mitted to be located remote from the other disconnecting 
means. If remot h install' - l in aa mdam e with this exi ep- 
tion, " phujut shall be posted at thi lot < tion oj the remain- 
ing grouped disconnects denoting its location. 

(B) Additional Service Disconnecting Means. The one or 

more additional service disconnecting means for fire 
pumps, emergency systems, legally required standby, or op- 
tional standby services permitted by 230.2 shall be installed 
remote from the one to six service disconnecting means for 
normal service to minimize the possibility of simultaneous 
interruption of supply. 

(C) Access to Occupants. In a multiple-occupancy build- 
ing, each occupant shall have access to the occupant's ser- 
vice disconnecting means. 

Exception: In a multiple-occupancy building where elec- 
tric service and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the service discon- 
necting means supplying more than one occupancy shall be 
permitted to be accessible to authorized management per- 
sonnel only. 

230.74 Simultaneous Opening of Poles. Each service dis- 
connect shall simultaneously disconnect all ungrounded 
service conductors that it controls from the premises wiring 

system. 

230.75 Disconnection of Grounded Conductor. Where 
the service disconnecting means does not disconnect the 
grounded conductor from the premises wiring, other means 
shall be provided for this purpose in the service equipment. 
A terminal or bus to which all grounded conductors can be 
attached by means of pressure connectors shall be permit- 
ted for this purpose. In a multisection switchboard, discon- 
nects for the grounded conductor shall be permitted to be in 
any section of the switchboard, provided any such switch- 
board section is marked. 

230.76 Manually or Power Operable. The service dis- 
connecting means for ungrounded service conductors shall 
consist of one of the following: 

(1) A manually operable switch or circuit breaker equipped 
with a handle or other suitable operating means 



(2) A power-operated switch or circuit breaker, provided 
the switch or circuit breaker can be opened by hand in 
the event of a power supply failure 

230.77 Indicating. The service disconnecting means shall 
plainly indicate whether it is in the open (off) or closed (on) 
position. 

230.79 Rating of Service Disconnecting Means. The ser- 
vice disconnecting means shall have a rating not less than 
the calculated load to be carried, determined in accordance 
with Part III, IV, or V of Article 220, as applicable. In no 
case shall the rating be lower than specified in 230.79(A). 
(B), (C), or (D). 

(A) One-Circuit Installations. For installations to supply 
only limited loads of a single branch circuit, the service 
disconnecting means shall have a rating of not less than 
15 amperes. 

(B) Two-Circuit Installations. For installations consisting 
of not more than two 2-wire branch circuits, the service 
disconnecting means shall have a rating of not less than 
30 amperes. 

(C) One-Family Dwellings. For a one-family dwelling, 
the service disconnecting means shall have a rating of not 
less than 100 amperes, 3-wire. 

(D) All Others. For all other installations, the service dis- 
connecting means shall have a rating of not less than 
60 amperes. 

230.80 Combined Rating of Disconnects. Where the ser- 
vice disconnecting means consists of more than one switch 
or circuit breaker, as permitted by 230.71, the combined 
ratings of all the switches or circuit breakers used shall not 
be less than the rating required by 230.79. 

230.81 Connection to Terminals. The service conductors 
shall be connected to the service disconnecting means by 
pressure connectors, clamps, or other approved means. 
Connections that depend on solder shall not be used. 

230.82 Equipment Connected to the Supply Side of Ser- 
vice Disconnect. Only the following equipment shall be 
permitted to be connected to the supply side of the service 
disconnecting means: 

(1) Cable limiters or other current-limiting devices. 

(2) Meters and meter sockets nominally rated not in excess 
of 600 volts, provided all metal housings and service 
enclosures are grounded in accordance with Part VII 
and bonded in accordance with Part V of Article 250. 

(3) Meter disconnect switches nominally rated not in ex- 
cess of 600 volts that have a short-circuit current rating 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-85 



230.90 



ARTICLE 230 — SERVICES 



equal to or greater than the available short-circuit cur- 
rent, provided all metal housings and service enclo- 
sures are grounded in accordance with Part VII and 
bonded in accordance with Part V of Article 250. A 
meter disconnect switch shall be capable of interrupt- 
ing the load served. 

(4) Instrument transformers (current and voltage), imped- 
ance shunts, load management devices, surge arresters, 
and Type 1 surge-protective devices. 

(5) Taps used only to supply load management devices, 
circuits for standby power systems, fire pump equip- 
ment, and fire and sprinkler alarms, if provided with 
service equipment and installed in accordance with re- 
quirements for service-entrance conductors. 

(6) Solar photovoltaic systems, fuel cell systems, or inter- 
connected electric power production sources. 

(7) Control circuits for power-operable service disconnect- 
ing means, if suitable overcurrent protection and dis- 
connecting means are provided. 

(8) Ground-fault protection systems or Type 2 surge- 
protective devices, where installed as part of listed 
equipment, if suitable overcurrent protection and dis- 
connecting means are provided. 

(9) Connections used only to supply j ; s!e>i communication . 
equipment undei the exclusive vvwA o! the serving 
electric utility, if suitable overcurrent protection and 
disconnecting means are provided. For installations of 
equipment by the serving electric iitilicv J disconnect- 
ing means is not required if trie suppl> is installed as 
pari of a meter socket, such ih-if access ctn only bs 
gained with the metei remo' s d 

VII. Service Equipment — Overcurrent Protection 

230.90 Where Required. Each ungrounded service con- 
ductor shall have overload protection. 

(A) Ungrounded Conductor. Such protection shall be pro- 
vided by an overcurrent device in series with each ungrounded 
service conductor that has a rating or setting not higher than 
the allowable ampacity of the conductor. A set of fuses shall 
be considered all the fuses required to protect all the un- 
grounded conductors of a circuit. Single-pole circuit breakers, 
grouped in accordance with 230.71(B), shall be considered as 
one protective device. 

Exception No. 1: For motor-starting currents, ratings that 
comply with 430.52, 430.62, and 430.63 shall be permitted. 

Exception No. 2: Fuses and circuit breakers with a rating 
or setting that complies with 240.4(B) or (C) and 240.6 
shall be permitted. 

Exception No. 3: Two to six circuit breakers or sets of fuses 
shall be permitted as the overcurrent device to provide the 



overload protection. The sum of the ratings of the circuit 
breakers or fuses shall be permitted to exceed the ampacity of 
the service conductors, provided the calculated load does not 
exceed the ampacity of the service conductors. 

Exception No. 4: Overload protection for fire pump supply 
conductors shall comply with 695.4(B)(2)(a). 

Exception No. 5: Overload protection for 120/240-volt, 
3-wire, single-phase dwelling services shall be permitted in 
accordance with the requirements of 310.15(B)(6). 

(B) Not in Grounded Conductor. No overcurrent device 
shall be inserted in a grounded service conductor except a 
circuit breaker that simultaneously opens all conductors of 
the circuit. 

230.91 Location. The service overcurrent device shall be 
an integral part of the service disconnecting means or shall 
be located immediately adjacent thereto. 

230.92 Locked Service Overcurrent Devices. Where the 
service overcurrent devices are locked or sealed or are not 
readily accessible to the occupant, branch-circuit or feeder 
overcurrent devices shall be installed on the load side, shall 
be mounted in a readily accessible location, and shall be of 
lower ampere rating than the service overcurrent device. 

230.93 Protection of Specific Circuits. Where necessary 
to prevent tampering, an automatic overcurrent device that 
protects service conductors supplying only a specific load, 
such as a water heater, shall be permitted to be locked or 
sealed where located so as to be accessible. 

230.94 Relative Location of Overcurrent Device and 
Other Service Equipment. The overcurrent device shall 
protect all circuits and devices. 

Exception No. 1: The service switch shall be permitted on 
the supply side. 

Exception No. 2: High-impedance shunt circuits, surge 
arresters, Type 1 surge-protective devices, surge-protective 
capacitors, and instrument transformers (current and volt- 
age) shall be permitted to be connected and installed on the 
supply side of the service disconnecting means as permitted 
by 230.82. 

Exception No. 3: Circuits for load management devices 
shall be permitted to be connected on the supply side of the 
service overcurrent device where separately provided, with 
overcurrent protection. 

Exception No. 4: Circuits used only for the operation of 
fire alarm, other protective signaling systems, or the supply 
to fire pump equipment shall be permitted to be connected 
on the supply side of the service overcurrent device where 
separately provided with overcurrent protection. 



70-86 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 230 — SERVICES 



230.204 



Exception No. 5: Meters nominally rated not in excess of 
600 volts shall be permitted, provided all metal housings 
and service enclosures are grounded. 

Exception No. 6: Where service equipment is power oper- 
able, the control circuit shall be permitted to be connected 
ahead of the service equipment if suitable overcurrent pro- 
tection and disconnecting means are provided. 

230.95 Ground-Fault Protection of Equipment. Ground- 
fault protection of equipment shall be provided for solidly 
grounded wye electric services of more than 150 volts to 
ground but not exceeding 600 volts phase-to-phase for each 
service disconnect rated 1000 amperes or more. The 
grounded conductor for the solidly grounded wye system 
shall be connected directly to ground through a grounding 
electrode system, as specified in 250.50, without inserting 
any resistor or impedance device. 

The rating of the service disconnect shall be considered 
to be the rating of the largest fuse that can be installed or 
the highest continuous current trip setting for which the 
actual overcurrent device installed in a circuit breaker is 
rated or can be adjusted. 

Exception: The ground-fault protection provisions of this 
section shall not apply to a service disconnect for a con- 
tinuous industrial process where a nonorderly shutdown 
will introduce additional or increased hazards. 

(A) Setting. The ground-fault protection system shall op- 
erate to cause the service disconnect to open all ungrounded 
conductors of the faulted circuit. The maximum setting of the 
ground-fault protection shall be 1200 amperes, and the maxi- 
mum time delay shall be one second for ground-fault currents 
equal to or greater than 3000 amperes. 

(B) Fuses. If a switch and fuse combination is used, the 
fuses employed shall be capable of interrupting any current 
higher than the interrupting capacity of the switch during a 
time that the ground-fault protective system will not cause 
the switch to open. 

(C) Performance Testing. The ground-fault protection 
system shall be performance tested when first installed on 
site. The test shall be conducted in accordance with instruc- 
tions that shall be provided with the equipment. A written 
record of this test shall be made and shall be available to 
the authority having jurisdiction. 

Informational Note No. 1: Ground-fault protection that 
functions to open the service disconnect affords no protec- 
tion from faults on the line side of the protective element. It 
serves only to limit damage to conductors and equipment 
on the load side in the event of an arcing ground fault on 
the load side of the protective element. 

Informational Note No. 2: This added protective equip- 
ment at the service equipment may make it necessary to 



review the overall wiring system for proper selective over- 
current protection coordination. Additional installations of 
ground-fault protective equipment may be needed on feed- 
ers and branch circuits where maximum continuity of elec- 
tric service is necessary. 

Informational Note No. 3: Where ground-fault protection 
is provided for the service disconnect and interconnection 
is made with another supply system by a transfer device, 
means or devices may be needed to ensure proper ground- 
fault sensing by the ground-fault protection equipment. 

Informational Note No. 4: See 517.17(A) for information 
on where an additional step of ground-fault protection is 
required for hospitals and other buildings with critical areas 
or life support equipment. 



VIII. Services Exceeding 600 Volts, Nominal 

230.200 General. Service conductors and equipment used 
on circuits exceeding 600 volts, nominal, shall comply with 
all the applicable provisions of the preceding sections of 
this article and with the following sections that supplement 
or modify the preceding sections. In no case shall the pro- 
visions of Part VIII apply to equipment on the supply side 
of the service point. 

Informational Note: For clearances of conductors of over 
600 volts, nominal, see ANSI C2-2007, National Electrical 
Safety Code. 

230.202 Service-Entrance Conductors. Service-entrance 
conductors to buildings or enclosures shall be installed to 
conform to 230.202(A) and (B). 

(A) Conductor Size. Service-entrance conductors shall not 
be smaller than 6 AWG unless in multiconductor cable. 
Multiconductor cable shall not be smaller than 8 AWG. 

(B) Wiring Methods. Service-entrance conductors shall 
be installed by one of the wiring methods covered in 
300.37 and 300.50. 

230.204 Isolating Switches. 

(A) Where Required. Where oil switches or air, oil, 
vacuum, or sulfur hexafluoride circuit breakers constitute the 
service disconnecting means, an isolating switch with visible 
break contacts shall be installed on the supply side of the 
disconnecting means and all associated service equipment. 

Exception: An isolating switch shall not be required where 
the circuit breaker or switch is mounted on removable truck 
panels or metal-enclosed switchgear units where both of 
the following conditions apply: 

(1) Cannot be opened unless the circuit is disconnected. 

(2) Where all energized parts are automatically discon- 
nected when the circuit breaker or switch is removed 
from the normal operating position. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-87 



230.205 



ARTICLE 240 — OVERCURRENT PROTECTION 



(B) Fuses as Isolating Switch. Where fuses are of the type 
that can be operated as a disconnecting switch, a set of such 
fuses shall be permitted as the isolating switch. 

(C) Accessible to Qualified Persons Only. The isolating 
switch shall be accessible to qualified persons only. 

(D) Connection to Ground. Isolating switches shall be 
provided with a means for readily connecting the load side 
conductors to a grounding electrode system, equipment 
ground busbar, or grounded steel structure when discon- 
nected from the source of supply. 

A means for grounding the load side conductors to a 
grounding electrode system, equipment grounding busbar, 
or grounded structural steel shall not be required for any 
duplicate isolating switch installed and maintained by the 
electric supply company. 

230.205 Disconnecting Means. 

(A) Location. The service disconnecting means shall be 
located in accordance with 230.70. 

For either overhead or underground primary distribu- 
tion systems on private property, the service disconnect 
shall be permitted to be located in a location that is not 
readily accessible, if the disconnecting means ai I.: upd- 
ated by mechanical linkage from a readily accessible point, 
or electronically in accordance with 230.205(C). v.-here ap- 
plicable. 

(B) IVpe. Each service disconnect shall simultaneously dis- 
connect all ungrounded service conductors that it controls and 
shall have a fault-closing rating that is not less than the maxi- 
mum short-circuit current available at its supply terminals. 

Where fused switches or separately mounted fuses are in- 
stalled, the fuse characteristics shall be permitted to contribute 
to the fault-closing rating of the disconnecting means. 

(C) Remote Control, or multibuilding, industrial installa- 
tions under single management, the service disconnecting 
means shall be permitted to be located at a separate build- 
ing or structure. In such cases, the service disconnecting 
means shall be permitted to be electrically operated by a 
readily accessible, remote-control device. 

230.206 Overcurrent Devices as Disconnecting Means. 

Where the circuit breaker or alternative for it, as specified 
in 230.208 for service overcurrent devices, meets the re- 
quirements specified in 230.205, they shall constitute the 
service disconnecting means. 

230.208 Protection Requirements. A short-circuit protec- 
tive device shall be provided on the load side of, or as an 
integral part of, the service disconnect, and shall protect all 
ungrounded conductors that it supplies. The protective device 
shall be capable of detecting and interrupting all values of 



current, in excess of its trip setting or melting point, that can 
occur at its location. A fuse rated in continuous amperes not to 
exceed three times the ampacity of the conductor, or a circuit 
breaker with a trip setting of not more than six times the 
ampacity of the conductors, shall be considered as providing 
the required short-circuit protection. 

Informational Note: See Table 310.60(0(67) through 
Table ?10.60(Cj(86) for ampacities of conductors rated 
2001 volts and above. 

Overcurrent devices shall conform to 230.208(A) and 
(B). 

(A) Equipment Type. Equipment used to protect service- 
entrance conductors shall meet the requirements of Article 
490, Part II. 

(B) Enclosed Overcurrent Devices. The restriction to 
80 percent of the rating for an enclosed overcurrent device 
for continuous loads shall not apply to overcurrent devices 
installed in systems operating at over 600 volts. 

230.209 Surge Arresters (Lightning Arresters). Surge 
arresters installed in accordance with the requirements of 
Article 280 shall be permitted on each ungrounded over- 
head service conductor. 

230.210 Service Equipment — General Provisions. Ser- 
vice equipment, including instrument transformers, shall 
conform to Article 490, Part I. 

230.211 Metal-Enclosed Switchgear. Metal-enclosed 
switchgear shall consist of a substantial metal structure 
and a sheet metal enclosure. Where installed over a combus- 
tible floor, suitable protection thereto shall be provided. 

230.212 Over 35,000 Volts. Where the voltage exceeds 
35,000 volts between conductors that enter a building, they 
shall terminate in a metal-enclosed switchgear compart- 
ment or a vault conforming to the requirements of 450.41 
through 450.48. 



ARTICLE 240 
( h erciirreis 1 Protection 



I. General 

240.1 Scope. Parts I through VII of this article provide the 
general requirements for overcurrent protection and over- 
current protective devices not more than 600 volts, nomi- 
nal. Part VIII covers overcurrent protection for those por- 
tions of supervised industrial installations operating at 



70-88 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.4 



voltages of not more than 600 volts, nominal. Part IX cov- 
ers overcurrent protection over 600 volts, nominal. 

Informational Note: Overcurrent protection for conductors 
and equipment is provided to open the circuit if the current 
reaches a value that will cause an excessive or dangerous 
temperature in conductors or conductor insulation. See also 
110.9 for requirements for interrupting ratings and 110.10 
for requirements for protection against fault currents. 

240.2 Definitions. 

Current-Limiting Overcurrent Protective Device. A de- 
vice that, when interrupting currents in its current-limiting 
range, reduces the current flowing in the faulted circuit to a 
magnitude substantially less than that obtainable in the 
same circuit if the device were replaced with a solid con- 
ductor having comparable impedance. 

Supervised Industrial Installation. For the purposes of 
Part VIII, the industrial portions of a facility where all of 
the following conditions are met: 

(1) Conditions of maintenance and engineering supervision 
ensure that only qualified persons monitor and service 
the system. 

(2) The premises wiring system has 2500 kVA or greater of 
load used in industrial process(es), manufacturing ac- 
tivities, or both, as calculated in accordance with Ar- 
ticle 220. 

(3) The premises has at least one service or feeder that is 
more than 1 50 volts to ground and more than 300 volts 
phase-to-phase. 

This definition excludes installations in buildings used by 
the industrial facility for offices, warehouses, garages, ma- 
chine shops, and recreational facilities that are not an integral 
part of the industrial plant, substation, or control center. 

Tap Conductors. As used in this article, a tap conductor is 
defined as a conductor, other than a service conductor, that 
has overcurrent protection ahead of its point of supply that 
exceeds the value permitted for similar conductors that are 
protected as described elsewhere in 240.4. 

240.3 Other Articles. Equipment shall be protected against 
overcurrent in accordance with the article in this Code that 
covers the type of equipment specified in Table 240.3. 

240.4 Protection of Conductors. Conductors, other than 
flexible cords, flexible cables, and fixture wires, shall be 
protected against overcurrent in accordance with their am- 
pacities specified in 310.15, unless otherwise permitted or 
required in 240.4(A) through (G). 

Informational Note: See IGEA P-32-382-2007 for infor- 
mation tin allowable short circuit eun n foi insulated 
coppei Mu) aluminum conductors 



Table 240.3 Other Articles 



Equipment 


Article 


Air-conditioning and refrigerating 


440 


equipment 




Appliances 


422 


Assembly occupancies 


518 


Audio signal processing, 


640 


amplification, and reproduction 




equipment 




Branch circuits 


210 


Busways 


368 


Capacitors 


460 


Class 1, Class 2, and Class 3 


725 


remote-control, signaling, and 




power-limited circuits 




Cranes and hoists 


610 


Electric signs and outline lighting 


600 


Electric welders 


630 


Electrolytic cells 


668 


Elevators, dumbwaiters, escalators, 


620 


moving walks, wheelchair lifts, and 




stairway chairlifts 




Emergency systems 


700 


Fire alarm systems 


760 


Fire pumps 


695 


Fixed electric heating equipment for 


427 


pipelines and vessels 




Fixed electric space-heating 


424 


equipment 




Fixed outdoor electric deicing and 


426 


snow-melting equipment 




Generators 


445 


Health care facilities 


517 


Induction and dielectric heating 


665 


equipment 




Industrial machinery 


670 


Luminaires, lampholders, and lamps 


410 


Motion picture and television studios 


530 


and similar locations 




Motors, motor circuits, and 


430 


controllers 




Phase converters 


455 


Pipe organs 


650 


Receptacles 


406 


Services 


230 


Solar photovoltaic systems 


690 


Switchboards and panelboards 


408 


Theaters, audience areas of motion 


520 


picture and television studios, and 




similar locations 




Transformers and transformer vaults 


450 


X-ray equipment 


660 



(A) Power Loss Hazard. Conductor overload protection 
shall not be required where the interruption of the circuit 
would create a hazard, such as in a material-handling mag- 
net circuit or fire pump circuit. Short-circuit protection 
shall be provided. 

Informational Note: See NFPA 20-2010, Standard for the 
Installation of Stationary Pumps for Fire Protection. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-89 



240.5 



ARTICLE 240 — OVERCURRENT PROTECTION 



(B) 0\ercurrenl Devices Rated 800 Amperes or Less. 
The next higher standard overcurrent device rating (above 
the ampacity of the conductors being protected) shall be 
permitted to be used, provided all of the following condi- 
tions are met: 

(1 ) The conductors being protected are not part of a branch 
circuit supplying more Shan one receptacle for cord- 
and-plug-connected portable loads. 

(2) The ampacity of the conductors does not correspond 
with the standard ampere rating of a fuse or a circuit 
breaker without overload trip adjustments above its rat- 
ing (but that shall be permitted to have other trip or 
rating adjustments). 

(3) The next higher standard rating selected does not ex- 
ceed 800 amperes. 

(C) Overcurrent Devices Rated over 800 Amperes. Where 
the overcurrent device is rated over 800 amperes, the am- 
pacity of the conductors it protects shall be equal to or 
greater than the rating of the overcurrent device defined in 
240.6. 

(D) Small Conductors. Unless specifically permitted in 
240.4(E) or (G), the overcurrent protection shall not exceed 
that required by (D)(1) through (D)(7) after any correction 
factors for ambient temperature and number of conductors 
have been applied. 

(1) 18 AWG Copper. 7 amperes, provided all the follow- 
ing conditions are met: 

(1) Continuous loads do not exceed 5.6 amperes. 

(2) Overcurrent protection is provided by one of the fol- 
lowing: 

a. Branch-circuit-rated circuit breakers listed and marked 
for use with 18 AWG copper wire 

b. Branch-circuit-rated fuses listed and marked for use 
with 18 AWG copper wire 

c. Class CC, Class J, or Class T fuses 

(2) 16 AWG Copper. 10 amperes, provided all the follow- 
ing conditions are met: 

(1) Continuous loads do not exceed 8 amperes. 

(2) Overcurrent protection is provided by one of the fol- 
lowing: 

a. Branch-circuit-rated circuit breakers listed and 
marked for use with 16 AWG copper wire 

b. Branch-circuit-rated fuses listed and marked for use 
with 1 6 AWG copper wire 

c. Class CC, Class J, or Class T fuses 

(3) 14 AWG Copper. 15 amperes 

(4) 12 AWG Aluminum and Copper-Clad Aluminum. 

15 amperes 



(5) 12 AWG Copper. 20 amperes 

(6) 10 AWG Aluminum and Copper-Clad Aluminum. 

25 amperes 

(7) 10 AWG Copper. 30 amperes 

(E) Tap Conductors. Tap conductors shall be permitted to 
be protected against overcurrent in accordance with the fol- 
lowing: 

(1) 210.19(A)(3) and (A)(4), Household Ranges and Cook- 
ing Appliances and Other Loads 

(2) 240.5(B)(2), Fixture Wire 

(3) 240.21, Location in Circuit 

(4) 368.17(B), Reduction in Ampacity Size of Busway 

(5) 368.17(C), Feeder or Branch Circuits (busway taps) 

(6) 430.53(D), Single Motor Taps 

(F) Transformer Secondary Conductors. Single-phase 
(other than 2-wire) and multiphase (other than delta-delta, 
3-wire) transformer secondary conductors shall not be consid- 
ered to be protected by the primary overcurrent protective 
device. Conductors supplied by the secondary side of a single- 
phase transformer having a 2-wire (single-voltage) secondary, 
or a three-phase, delta-delta connected transformer having a 
3-wire (single-voltage) secondary, shall be permitted to be 
protected by overcurrent protection provided on the primary 
(supply) side of the transformer, provided this protection is in 
accordance with 450.3 and does not exceed the value deter- 
mined by multiplying the secondary conductor ampacity by 
the secondary-to-primary transformer voltage ratio. 

(G) Overcurrent Protection for Specific Conductor Ap- 
plications. Overcurrent protection for the specific conduc- 
tors shall be permitted to be provided as referenced in Table 
240.4(G). 

240.5 Protection of Flexible Cords, Flexible Cables, and 
Fixture Wires. Flexible cord and flexible cable, including 
tinsel cord and extension cords, and fixture wires shall be 
protected against overcurrent by either 240.5(A) or (B). 

(A) Ampacities. Flexible cord and flexible cable shall be 
protected by an overcurrent device in accordance with their 
ampacity as specified in Table 400.5(A)(1) and Table 
400.5(A)(2). Fixture wire shall be protected against overcur- 
rent in accordance with its ampacity as specified in Table 
402.5. Supplementary overcurrent protection, as covered in 
240.10, shall be permitted to be an acceptable means for pro- 
viding this protection. 

(B) Branch-Circuit Overcurrent Device. Flexible cord 
shall be protected, where supplied by a branch circuit, in ac- 
cordance with one of the methods described in 240.5(B)(1), 
(B)(3), or (B)(4). Fixture wire shall be protected, where sup- 
plied by a branch circuit, in accordance with 240.5(B)(2). 



70-90 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.10 



Table 240.4(G) Specific Conductor Applications 



Conductor 


Article 


Section 


Air-conditioning and 


440, Parts III, 




refrigeration 


VI 




equipment circuit 






conductors 






Capacitor circuit 


460 


460.8(B) and 


conductors 




460.25(A)-(D) 


Control and 


727 


727.9 


instrumentation 






circuit conductors 






(Type ITC) 






Electric welder 


630 


630.12 and 630.32 


circuit conductors 






Fire alarm system 


760 


760.43, 760.45, 


circuit conductors 




760.121, and Chapter 

9, Tables 12(A) and 

12(B) 


Motor-operated 


422, Part II 




appliance circuit 






conductors 






Motor and 


430, Parts III, 




motor-control 


IV, V, VI, VII 




circuit conductors 






Phase converter 


455 


455.7 


supply conductors 






Remote-control, 


725 


725.43, 725.45, 


signaling, and 




725.121, and Chapter 


power-limited 




9, Tables 11(A) and 


circuit conductors 




11(B) 


Secondary tie 


450 


450.6 


conductors 







(1) Supply Cord of Listed Appliance or Luminaire. 

Where flexible cord or tinsel cord is approved for and used 
with a specific listed appliance or luminaire, it shall be 
considered to be protected when applied within the appli- 
ance or luminaire listing requirements. For the purposes of 
this section, a luminaire may be either portable or perma- 
nent. 

(2) Fixture Wire. Fixture wire shall be permitted to be 
tapped to the branch-circuit conductor of a branch circuit in 
accordance with the following: 

(1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of 
run length 

(2) 20-ampere circuits 
run length 

(3) 20-ampere circuits 

(4) 30-ampere circuits 

(5) 40-ampere circuits 

(6) 50-ampere circuits 



16 AWG, up to 30 m (100 ft) of 

14 AWG and larger 
14 AWG and larger 
1 2 AWG and larger 
12 AWG and larger 



(3) Extension Cord Sets. Flexible cord used in listed ex- 
tension cord sets shall be considered to be protected when 
applied within the extension cord listing requirements. 



(4) Field Assembled Extension Cord Sets. Flexible cord 
used in extension cords made with separately listed and 
installed components shall be permitted to be supplied by a 
branch circuit in accordance with the following: 
20-ampere circuits — 16 AWG and larger 

240.6 Standard Ampere Ratings. 

(A) Fuses and Fixed-Trip Circuit Breakers. The stan- 
dard ampere ratings for fuses and inverse time circuit 
breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 
60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 
350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 
2500, 3000, 4000, 5000, and 6000 amperes. Additional 
standard ampere ratings for fuses shall be 1, 3, 6, 10, and 
601. The use of fuses and inverse time circuit breakers with 
nonstandard ampere ratings shall be permitted. 

(B) Adjustable-Trip Circuit Breakers. The rating of 
adjustable-trip circuit breakers having external means for 
adjusting the current setting (long-time pickup setting), not 
meeting the requirements of 240.6(C), shall be the maxi- 
mum setting possible. 

(C) Restricted Access Adjustable-Trip Circuit Break- 
ers. A circuit breaker(s) that has restricted access to the 
adjusting means shall be permitted to have an ampere rat- 
ing^) that is equal to the adjusted current setting (long-time 
pickup setting). Restricted access shall be defined as lo- 
cated behind one of the following: 

(1) Removable and sealable covers over the adjusting means 

(2) Bolted equipment enclosure doors 

(3) Locked doors accessible only to qualified personnel 

240.8 Fuses or Circuit Breakers in Parallel. Fuses and 

circuit breakers shall be permitted to be connected in par- 
allel where they are factory assembled in parallel and listed 
as a unit. Individual fuses, circuit breakers, or combinations 
thereof shall not otherwise be connected in parallel. 

240.9 Thermal Devices. Thermal relays and other devices 
not designed to open short circuits or ground faults shall 
not be used for the protection of conductors against over- 
current due to short circuits or ground faults, but the use of 
such devices shall be permitted to protect motor branch- 
circuit conductors from overload if protected in accordance 
with 430.40. 

240.10 Supplementary Overcurrent Protection. Where 
supplementary overcurrent protection is used for luminaires, 
appliances, and other equipment or for internal circuits and 
components of equipment, it shall not be used as a substitute 
for required branch-circuit overcurrent devices or in place of 
the required branch-circuit protection. Supplementary overcur- 
rent devices shall not be required to be readily accessible. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-91 



240.12 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.12 Electrical System Coordination. Where an or- 
derly shutdown is required to minimize the hazard(s) to 
personnel and equipment, a system of coordination based 
on the following two conditions shall be permitted: 

(1) Coordinated short-circuit protection 

(2) Overload indication based on monitoring systems or 
devices 

Informational Note: The monitoring system may cause the 
condition to go to alarm, allowing corrective action or an 
orderly shutdown, thereby minimizing personnel hazard 
and equipment damage. 

240.13 Ground-Fault Protection of Equipment. Ground- 
fault protection of equipment shall be provided in accor- 
dance with the provisions of 230.95 for solidly grounded 
wye electrical systems of more than 150 volts to ground but 
not exceeding 600 volts phase-to-phase for each individual 
device used as a building or structure main disconnecting 
means rated 1000 amperes or more. 

The provisions of this section shall not apply to the 
disconnecting means for the following: 

(1) Continuous industrial processes where a nonorderly shut- 
down will introduce additional or increased hazards 

(2) Installations where ground-fault protection is provided 
by other requirements for services or feeders 

(3) Fire pumps 

240.15 Ungrounded Conductors. 

(A) Overcurrent Device Required. A fuse or an overcur- 
rent trip unit of a circuit breaker shall be connected in 
series with each ungrounded conductor. A combination of a 
current transformer and overcurrent relay shall be consid- 
ered equivalent to an overcurrent trip unit. 

Informational Note: For motor circuits, see Parts III, IV, V, 
and XI of Article 430. 

(B) Circuit Breaker as Overcurrent Device. Circuit break- 
ers shall open all ungrounded conductors of the circuit both 
manually and automatically unless otherwise permitted in 

240.15(B)(1), (B)(2), (B)(3), and (B)(4). 

(1) Multiwire Branch Circuit. IndV'-mul single-pole cir- 
cuit breakers, with identified handle ties, shall be permitted 
as the protection for each ungrounded conductor of multi- 
wire branch circuits that serve only single-phase line-to- 
neutral loads. 

(2) Grounded Single-Phase Alternating-Current Cir- 
cuits. In grounded systems, individual single-pole circuit 
breakers rated 1 20/240 volts ac, with identified handle ties, 
shall be permitted as the protection for each ungrounded 
conductor for line-to-line connected loads for single-phase 
circuits. 



(3) 3-Phase and 2-Phase Systems. For line-to-line loads 
in 4-wire, 3-phase systems or 5-wire, 2-phase systems, in- 
dividual single-pole circuit breakers rated 120/240 volts ac 
with identified handle ties shall be permitted as the protec- 
tion for each ungrounded conductoi. if the " stem: have a 
grounded neutral poinl and the voltage to ground does not 
exceed 120 volts. 

(4) 3-W'irc- Direct-Current Circuits. Individual single- 
pole circuit breakers rated 125/2 i0 volts <V with identified 
handle tie 'Jul' be permitted as the piuUrtion for each 
ungrounded conductoi foi line-to line connected L-ads for 
3-wire, di s< i z\ rreni cir< mi-, .if fiitd Irui.i a s) i. m with 
a grounded neutral where the voltai" j to ground does not 
exceed 1 25 volts. 

II. Location 

240.21 Location in Circuit. Overcurrent protection shall 
be provided in each ungrounded circuit conductor and shall 
be located at the point where the conductors receive their 
supply except as specified in 240.21(A) through (H). Conduc- 
tors supplied under the provisions of 240.21(A) through (H) 
shall not supply another conductor except through an overcur- 
rent protective device meeting the requirements of 240.4. 

(A) Branch-Circuit Conductors. Branch-circuit tap con- 
ductors meeting the requirements specified in 210.19 shall 
be permitted to have overcurrent protection as specified in 
210.20. 

(B) Feeder Taps. Conductors shall be permitted to be tapped, 
without overcurrent protection at the tap, to a feeder as speci- 
fied in 240.21(B)(1) through (B)(5). The provisions of 
240.4(B) shall not be permitted for tap conductors. 

(1) Taps Not over 3 m (10 ft) Long. It the length of the 
tap conductors does not exceed 3 m (10 ft) and the tap 
conductors comply with all of the following: 

(1) The ampacity of the tap conductors is 

a. Not less than the combined calculated loads on the 
circuits supplied by the tap conductors, and 

b. Not less than the rating of the device supplied by 
the tap conductors or not less than the rating of the 
overcurrent protective device at the termination of 
the tap conductors. 

(2) The tap conductors do not extend beyond the switch- 
board, panelboard, disconnecting means, or control de- 
vices they supply. 

(3) Except at the point of connection to the feeder, the tap 
conductors are enclosed in a raceway, which shall ex- 
tend from the tap to the enclosure of an enclosed 
switchboard, panelboard, or control devices, or to the 
back of an open switchboard. 



70-92 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.21 



(4) For field installations, if the tap conductors leave the 
enclosure or vault in which the tap is made, the amp ic- 
ily of the tap conductors is not less Ihan orsc-lenth of 
the rating of the overcurrent device protecting the 
feedci conductors. 

Informational Note: For overcurrent protection require- 
ments for panelboards, see 408.36. 

(2) Taps Not over 7.5 m (25 ft) Long. Where the length of 
the tap conductors does not exceed 7.5 m (25 ft) and the tap 
conductors comply with all the following: 

(1) The ampacity of the tap conductors is not less than 
one-third of the rating of the overcurrent device pro- 
tecting the feeder conductors. 

(2) The tap conductors terminate in a single circuit breaker 
or a single set of fuses that limit the load to the ampac- 
ity of the tap conductors. This device shall be permitted 
to supply any number of additional overcurrent devices 
on its load side. 

(3) The tap conductors are protected from physical damage 
by being enclosed in an approved raceway or by other 
approved means. 

(3) Taps Supplying a Transformer [Primary Plus Sec- 
ondary Not over 7.5 m (25 ft) Long]. Where the tap con- 
ductors supply a transformer and comply with all the fol- 
lowing conditions: 

(1) The conductors supplying the primary of a transformer 
have an ampacity at least one-third the rating of the 
overcurrent device protecting the feeder conductors. 

(2) The conductors supplied by the secondary of the trans- 
former shall have an ampacity that is not less than the 
value of the primary-to-secondary voltage ratio multi- 
plied by one-third of the rating of the overcurrent de- 
vice protecting the feeder conductors. 

(3) The total length of one primary plus one secondary con- 
ductor, excluding any portion of the primary conductor 
that is protected at its ampacity, is not over 7.5 m (25 ft). 

(4) The primary and secondary conductors are protected 
from physical damage by being enclosed in an ap- 
proved raceway or by other approved means. 

(5) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(4) Taps over 7.5 m (25 ft) Long. Where the feeder is in a 
high bay manufacturing building over 11 m (35 ft) high at 
walls and the installation complies with all the following 
conditions: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons service the systems. 



(2) The tap conductors are not over 7.5 m (25 ft) long 
horizontally and not over 30 m (100 ft) total length. 

(3) The ampacity of the tap conductors is not less than 
one-third the rating of the overcurrent device protecting 
the feeder conductors. 

(4) The tap conductors terminate at a single circuit breaker 
or a single set of fuses that limit the load to the ampac- 
ity of the tap conductors. This single overcurrent de- 
vice shall be permitted to supply any number of addi- 
tional overcurrent devices on its load side. 

(5) The tap conductors are protected from physical damage 
by being enclosed in an approved raceway or by other 
approved means. 

(6) The tap conductors are continuous from end-to-end and 
contain no splices. 

(7) The tap conductors are sized 6 AWG copper or 4 AWG 
aluminum or larger. 

(8) The tap conductors do not penetrate walls, floors, or 
ceilings. 

(9) The tap is made no less than 9 m (30 ft) from the floor. 

(5) Outside Taps of Unlimited Length. Where the con 
ductors are located outdoors of a building or structure, ex- 
cept at the point of load termination, and comply with all of 
the following conditions: 

(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(C) Transformer Secondary Conductors. A set of con- 
ductors feeding a single load, or each set of conductors 
feeding separate loads, shall be permitted to be connected 
to a transformer secondary, without overcurrent protection 
at the secondary, as specified in 240.21(C)(1) through 
(C)(6). The provisions of 240.4(B) shall not be permitted 
for transformer secondary conductors. 

Informational Note: For overcurrent protection require- 
ments for transformers, see 450.3. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-93 



240.21 



ARTICLE 240 — OVERCURRENT PROTECTION 



(1) Protection by Primary Overcurrent Device. Conduc- 
tors supplied by the secondary side of a single-phase trans- 
former having a 2-wire (single-voltage) secondary, or a 
three-phase, delta-delta connected transformer having a 
3-wire (single-voltage) secondary, shall be permitted to be 
protected by overcurrent protection provided on the primary 
(supply) side of the transformer, provided this protection is in 
accordance with 450.3 and does not exceed the value deter- 
mined by multiplying the secondary conductor ampacity by 
the secondary-to-primary transformer voltage ratio. 

Single-phase (other than 2-wire) and multiphase (other 
than delta-delta, 3-wire) transformer secondary conductors 
are not considered to be protected by the primary overcur- 
rent protective device. 

(2) Transformer Secondary Conductors Not over 3 m 
(10 ft) Long. If the length of secondary conductor does not 
exceed 3 m (10 ft) and complies with all of the following: 

(1) The ampacity of the secondary conductors is 

a. Not less than the combined calculated loads on the 
circuits supplied by the secondary conductors, and 

b. Not less than the rating of the device supplied by 
the secondary conductors or not less than the rating 
of the overcurrent-protective device at the termina- 
tion of the secondary conductors 

(2) The secondary conductors do not extend beyond the 
switchboard, panelboard, disconnecting means, or con- 
trol devices they supply. 

(3) The secondary conductors are enclosed in a raceway, 
which shall extend from the transformer to the enclo- 
sure of an enclosed switchboard, panelboard, or control 
devices or to the back of an open switchboard. 

(4) For field installations where the secondary conductors 
leave the enclosure or vault in which the supply con- 
nection is made, the rating of the overcurrent device 
protecting the primary of the transformer, multiplied by 
the primary to secondary transformer voltage ratio, 
shall not exceed 10 times the ampacity of the second- 
ary conductor. 

Informational Note: For overcurrent protection require- 
ments for panelboards, see 408.36. 

(3) Industrial Installation Secondary Conductors Not 
over 7.5 m (25 ft) Long. For industrial installations only, 
where the length of the secondary conductors does not ex- 
ceed 7.5 m (25 ft) and complies with all of the following: 

(1) Conditions of maintenance and supervision ensure that 
only qualified persons service the systems. 

(2) The ampacity of the secondary conductors is not less 
than the secondary current rating of the transformer, 
and the sum of the ratings of the overcurrent devices does 
not exceed the ampacity of the secondary conductors. 

(3) All overcurrent devices are grouped. 



(4) The secondary conductors are protected from physical 
damage by being enclosed in an approved raceway or 
by other approved means. 

(4) Outside Secondary Conductors. Where the conduc- 
tors are located outdoors of a building or structure, except 
at the point of load termination, and comply with all of the 
following conditions: 

(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The conductors terminate at a single circuit breaker or 
a single set of fuses that limit the load to the ampacity 
of the conductors. This single overcurrent device shall 
be permitted to supply any number of additional over- 
current devices on its load side. 

(3) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(4) The disconnecting means for the conductors is installed 
at a readily accessible location complying with one of 
the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 

(5) Secondary Conductors from a Feeder Tapped 
Transformer. Transformer secondary conductors installed 
in accordance with 240.21(B)(3) shall be permitted to have 
overcurrent protection as specified in that section. 

(6) Secondary Conductors Not over 7.5 m (25 ft) Long. 

Where the length of secondary conductor does not exceed 
7.5 m (25 ft) and complies with all of the following: 

(1) The secondary conductors shall have an ampacity that is 
not less than the value of the primary-to-secondary volt- 
age ratio multiplied by one-third of the rating of the over- 
current device protecting the primary of the transformer. 

(2) The secondary conductors terminate in a single circuit 
breaker or set of fuses that limit the load current to not 
more than the conductor ampacity that is permitted by 
310.15. 

(3) The secondary conductors are protected from physical 
damage by being enclosed in an approved raceway or 
by other approved means. 

(D) Service Conductors. Service conductors shall be per- 
mitted to be protected by overcurrent devices in accordance 
with 230.91. 

(E) Busway Taps. Busways and busway taps shall be per- 
mitted to be protected against overcurrent in accordance 
with 368.17. 



70-94 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.32 



(F) Motor Circuit Taps. Motor-feeder and branch-circuit 
conductors shall be permitted to be protected against over- 
current in accordance with 430.28 and 430.53, respectively. 

(G) Conductors from Generator Terminals. Conductors 
from generator terminals that meet the size requirement in 
445.13 shall be permitted to be protected against overload 
by the generator overload protective device(s) required by 
445.12. 

(H) Battery Conductors. Overcurrent protection shall be 
permitted to be installed as close as practicable to the stor- 
age battery terminals in an unclassified location. Installa- 
tion of the overcurrent protection within a hazardous (clas 
sified) location shall also be permitted. 

240.22 Grounded Conductor. No overcurrent device shall 
be connected in series with any conductor that is intentionally 
grounded, unless one of the following two conditions is met: 

(1) The overcurrent device opens all conductors of the cir- 
cuit, including the grounded conductor, and is designed 
so that no pole can operate independently. 

(2) Where required by 430.36 or 430.37 for motor over- 
load protection. 

240.23 Change in Size of Grounded Conductor. Where a 
change occurs in the size of the ungrounded conductor, a 
similar change shall be permitted to be made in the size of 
the grounded conductor. 

240.24 Location in or on Premises. 

(A) Accessibility. Overcurrent devices shall be readily ac- 
cessible and shall be installed so that the center of the grip 
of the operating handle of the switch or circuit breaker, 
when in its highest position, is not more than 2.0 m (6 ft 
7 in.) above the floor or working platform, unless one of the 
following applies: 

(1) For busways, as provided in 368.17(C). 

(2) For supplementary overcurrent protection, as described 
in 240.10. 

(3) For overcurrent devices, as described in 225.40 and 
230.92. 

(4) For overcurrent devices adjacent to utilization equip- 
ment that they supply, access shall be permitted to be 
by portable means. 

(B) Occupancy. Each occupant shall have ready access to 
all overcurrent devices protecting the conductors supplying 
that occupancy, unless otherwise permitted in 240.24(B)(1) 
and (B)(2). 

(1) Service and Feeder Overcurrent Devices. Where elec- 
tric service and electrical maintenance are provided by the 
building management and where these are under continuous 



building management supervision, the service overcurrent de- 
vices and feeder overcurrent devices supplying more than one 
occupancy shall be permitted to be accessible only to autho- 
rized management personnel in the following: 

(1) Multiple-occupancy buildings 

(2) Guest rooms or guest suites 

(2) Branch-Circuit Overcurrent Devices. Where electric 
service and electrical maintenance are provided by the 
building management and where these are under continu- 
ous building management supervision, the branch-circuit 
overcurrent devices supplying any guest rooms or guest 
suites without permanent provisions for cooking shall be 
permitted to be accessible only to authorized management 
personnel. 

(C) Not Exposed to Physical Damage. Overcurrent de- 
vices shall be located where they will not be exposed to 
physical damage. 

Informational Note: See 110.11, Deteriorating Agents. 

(D) Not in Vicinity of Easily Ignitible Material. Overcur- 
rent devices shall not be located in the vicinity of easily 
ignitible material, such as in clothes closets. 

(E) Not Located in Bathrooms. In dwelling units, dormi- 
!■: tries, and guest rooms or guest suites, overcurrent devices, 
other than supplementary overcurrent protection, shall not 
be located in bathrooms. 

(F) Not Located over Steps. Overcurrent devices shall not 
be located over steps of a stairway. 

III. Enclosures 
240.30 General. 

(A) Protection from Physical Damage. Overcurrent de- 
vices shall be protected from physical damage by one of the 
following: 

(1) Installation in enclosures, cabinets, cutout boxes, or 
equipment assemblies 

(2) Mounting on open-type switchboards, panelboards, or 
control boards that are in rooms or enclosures free from 
dampness and easily ignitible material and are acces- 
sible only to qualified personnel 

(B) Operating Handle. The operating handle of a circuit 
breaker shall be permitted to be accessible without opening 
a door or cover. 

240.32 Damp or Wet Locations. Enclosures for overcur- 
rent devices in damp or wet locations shall comply with 
312.2. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-95 



240.33 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.33 Vertical Position. Enclosures for overcurrent de- 
vices shall be mounted in a vertical position unless that is 
shown to be impracticable. Circuit breaker enclosures shall be 
permitted to be installed horizontally where the circuit breaker 
is installed in accordance with 240.81. Listed busway plug-in 
units shall be permitted to be mounted in orientations corre- 
sponding to the busway mounting position. 

IV. Disconnecting and Guarding 

240.40 Disconnecting Means for Fuses. Cartridge fuses 
in circuits of any voltage where accessible to other than 
qualified persons, and all fuses in circuits over 150 volts to 
ground, shall be provided with a disconnecting means on 
their supply side so that each circuit containing fuses can be 
independently disconnected from the source of power. A 
current-limiting device without a disconnecting means shall 
be permitted on the supply side of the service disconnecting 
means as permitted by 230.82. A single disconnecting 
means shall be permitted on the supply side of more than 
one set of fuses as permitted by 430.112, Exception, for 
group operation of motors and 424.22(C) for fixed electric 
space-heating equipment. 

240.41 Arcing or Suddenly Moving Parts. Arcing or sud- 
denly moving parts shall comply with 240.41(A) and (B). 

(A) Location. Fuses and circuit breakers shall be located 
or shielded so that persons will not be burned or otherwise 
injured by their operation. 

(B) Suddenly Moving Parts. Handles or levers of circuit 
breakers, and similar parts that may move suddenly in such 
a way that persons in the vicinity are likely to be injured by 
being struck by them, shall be guarded or isolated. 

V. Plug Fuses, Fuseholders, and Adapters 
240.50 General. 

(A) Maximum Voltage. Plug fuses shall be permitted to 
be used in the following circuits: 

(1) Circuits not exceeding 125 volts between conductors 

(2) Circuits supplied by a system having a grounded neu- 
tral point where the line-to-neutral voltage does not 
exceed 150 volts 

(B) Marking. Each fuse, fuseholder, and adapter shall be 
marked with its ampere rating. 

(C) Hexagonal Configuration. Plug fuses of 15-ampere 
and lower rating shall be identified by a hexagonal configu- 
ration of the window, cap, or other prominent part to dis- 
tinguish them from fuses of higher ampere ratings. 



(D) No Energized Parts. Plug fuses, fuseholders, and 
adapters shall have no exposed energized parts after fuses 
or fuses and adapters have been installed. 

(E) Screw Shell. The screw shell of a plug-type fuseholder 
shall be connected to the load side of the circuit. 

240.51 Edison-Base Fuses. 

(A) Classification. Plug fuses of the Edison-base type shall 
be classified at not over 125 volts and 30 amperes and below. 

(B) Replacement Only. Plug fuses of the Edison-base type 
shall be used only for replacements in existing installations 
where there is no evidence of overfusing or tampering. 

240.52 Edison-Base Fuseholders. Fuseholders of the 
Edison-base type shall be installed only where they are 
made to accept Type S fuses by the use of adapters. 

240.53 Type S Fuses. Type S fuses shall be of the plug 
type and shall comply with 240.53(A) and (B). 

(A) Classification. Type S fuses shall be classified at not 
over 125 volts and to 15 amperes, 16 to 20 amperes, and 
21 to 30 amperes. 

(B) Noninterchangeable. Type S fuses of an ampere clas- 
sification as specified in 240.53(A) shall not be inter- 
changeable with a lower ampere classification. They shall 
be designed so that they cannot be used in any fuseholder 
other than a Type S fuseholder or a fuseholder with a Type 
S adapter inserted. 

240.54 Type S Fuses, Adapters, and Fuseholders. 

(A) To Fit Edison-Base Fuseholders. Type S adapters 
shall fit Edison-base fuseholders. 

(B) To Fit Type S Fuses Only. Type S fuseholders and 
adapters shall be designed so that either the fuseholder it- 
self or the fuseholder with a Type S adapter inserted cannot 
be used for any fuse other than a Type S fuse. 

(C) Nonremovable. Type S adapters shall be designed so 
that once inserted in a fuseholder, they cannot be removed. 

(D) Nontamperable. Type S fuses, fuseholders, and adapt- 
ers shall be designed so that tampering or shunting (bridg- 
ing) would be difficult. 

(E) Interchangeability. Dimensions of Type S fuses, fuse- 
holders, and adapters shall be standardized to permit inter- 
changeability regardless of the manufacturer. 



70-96 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.85 



VI. Cartridge Fuses and Fuseholders 
240.60 General. 

(A) Maximum Voltage — 300- Volt Type. Cartridge fuses 
and fuseholders of the 300-volt type shall be permitted to 
be used in the following circuits: 

(1) Circuits not exceeding 300 volts between conductors 

(2) Single-phase line-to-neutral circuits supplied from a 
3-phase, 4-wire, solidly grounded neutral source where 
the line-to-neutral voltage does not exceed 300 volts 

(B) Noninterchangeable — 0-6000-Ampere Cartridge 
Fuseholders. Fuseholders shall be designed so that it will 
be difficult to put a fuse of any given class into a fuseholder 
that is designed for a current lower, or voltage higher, than 
that of the class to which the fuse belongs. Fuseholders for 
current-limiting fuses shall not permit insertion of fuses 
that are not current-limiting. 

(C) Marking. Fuses shall be plainly marked, either by 
printing on the fuse barrel or by a label attached to the 
barrel showing the following: 

(1) Ampere rating 

(2) Voltage rating 

(3) Interrupting rating where other than 10,000 amperes 

(4) Current limiting where applicable 

(5) The name or trademark of the manufacturer 

The interrupting rating shall not be required to be marked 
on fuses used for supplementary protection. 

(D) Renewable Fuses. Class H cartridge fuses of the re- 
newable type shall be permitted to be used only for replace- 
ment in existing installations where there is no evidence of 
overfusing or tampering. 

240.61 Classification. Cartridge fuses and fuseholders 
shall be classified according to voltage and amperage 
ranges. Fuses rated 600 volts, nominal, or less shall be 
permitted to be used for voltages at or below their ratings. 

VII. Circuit Breakers 

240.80 Method of Operation. Circuit breakers shall be 
trip free and capable of being closed and opened by manual 
operation. Their normal method of operation by other than 
manual means, such as electrical or pneumatic, shall be 
permitted if means for manual operation are also provided. 

240.81 Indicating. Circuit breakers shall clearly indicate 
whether they are in the open "off or closed "on" position. 

Where circuit breaker handles are operated vertically 
rather than rotationally or horizontally, the "up" position of 
the handle shall be the "on" position. 



240.82 Nontamperable. A circuit breaker shall be of such 
design that any alteration of its trip point (calibration) or 
the time required for its operation requires dismantling of 
the device or breaking of a seal for other than intended 
adjustments. 

240.83 Marking. 

(A) Durable and Visible. Circuit breakers shall be marked 
with their ampere rating in a manner that will be durable 
and visible after installation. Such marking shall be permit- 
ted to be made visible by removal of a trim or cover. 

(B) Location. Circuit breakers rated at 100 amperes or less 
and 600 volts or less shall have the ampere rating molded, 
stamped, etched, or similarly marked into their handles or 
escutcheon areas. 

(C) Interrupting Rating. Every circuit breaker having an 
interrupting rating other than 5000 amperes shall have its 
interrupting rating shown on the circuit breaker. The inter- 
rupting rating shall not be required to be marked on circuit 
breakers used for supplementary protection. 

(D) Used as Switches. Circuit breakers used as switches in 
120-volt and 277-volt fluorescent lighting circuits shall be 
listed and shall be marked SWD or HID. Circuit breakers 
used as switches in high-intensity discharge lighting cir- 
cuits shall be listed and shall be marked as HID. 

(E) Voltage Marking. Circuit breakers shall be marked 
with a voltage rating not less than the nominal system volt- 
age that is indicative of their capability to interrupt fault 
currents between phases or phase to ground. 

240.85 Applications. A circuit breaker with a straight volt- 
age rating, such as 240V or 480V, shall be permitted to be 
applied in a circuit in which the nominal voltage between 
any two conductors does not exceed the circuit breaker's 
voltage rating. A two-pole circuit breaker shall not be used 
for protecting a 3-phase, corner-grounded delta circuit un- 
less the circuit breaker is marked 1<J> — 3((> to indicate such 
suitability. 

A circuit breaker with a slash rating, such as 120/240V 
or 480Y/277V, shall be permitted to be applied in a solidly 
grounded circuit where the nominal voltage of any conduc- 
tor to ground does not exceed the lower of the two values 
of the circuit breaker's voltage rating and the nominal volt- 
age between any two conductors does not exceed the higher 
value of the circuit breaker's voltage rating. 

Informational Note: Proper application of molded case cir- 
cuit breakers on 3-phase systems, other than solidly 
grounded wye, particularly on corner grounded delta sys- 
tems, considers the circuit breakers' individual pole- 
interrupting capability. 



201 1 Edition NATIONAL ELECTRICAL CODE 



70-97 



240.86 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.86 Series Ratings. Where a circuit breaker is used on 
a circuit having an available fault current higher than the 
marked interrupting rating by being connected on the load 
side of an acceptable overcurrent protective device having a 
higher rating, the circuit breaker shall meet the require- 
ments specified in (A) or (B), and (C). 

(A) Selected Under Engineering Supervision in Existing 
Installations. The series rated combination devices shall be 
selected by a licensed professional engineer engaged pri- 
marily in the design or maintenance of electrical installa- 
tions. The selection shall be documented and stamped by 
the professional engineer. This documentation shall be 
available to those authorized to design, install, inspect, 
maintain, and operate the system. This series combination 
rating, including identification of the upstream device, shall 
be field marked on the end use equipment. 

For calculated applications, the engineer shall ensure 
that the downstream circuit breaker(s) that are part of the 
series combination remain passive during the interruption 
period of the line side fully rated, current- limiting device. 

(B) Tested Combinations. The combination of line-side 
overcurrent device and load-side circuit breaker(s) is tested 
and marked on the end use equipment, such as switch- 
boards and panelboards. 

Informational Note to (A) and (B): See 110.22 for marking of 
series combination systems. 

(C) Motor Contribution. Series ratings shall not be used 
where 

(1) Motors are connected on the load side of the higher- 
rated overcurrent device and on the line side of the 
lower-rated overcurrent device, and 

(2) The sum of the motor full-load currents exceeds 1 per- 
cent of the interrupting rating of the lower-rated circuit 
breaker. 

240.87 Noninslantaneous Trip. Where a e rcuit breake is 
used without an instantaneous trip, documentation shall be 
available: to those authorized to design install, operate oi >o 
spect the installation < tothe local in of the circuit breaker(s). 
Where a circui: break© is utilized without an instanta- 
neous trip, one of the following or approved equivalent 
means shall be provided: 

(1) Zone-selective interlocking 

(2) Differential relaying 

(3) Energy-reduaui,- maintenance switching with local sta- 
tus indicator 

Informational Note: An ;nergy-reducihg maint nana smt^h 
ill owe a worker t< set a circui breaker trip unit to no iM>"i- 
tiotial delay' to reduce the clearing time while the w'cdkei is 
working within ,n arc-flash bound'arj a: defined <n 
NFPA 70E-2009, Standard, foi Electrical Safety in tin Work- 
place, and then lo >cl tile trip unil kick to a normal selliin: 
• n ■• th potential!) I> i trdous work is ;oi ij |ek 



VIII. Supervised Industrial Installations 

240.90 General. Overcurrent protection in areas of super- 
vised industrial installations shall comply with all of the 
other applicable provisions of this article, except as pro- 
vided in Part VIII. The provisions of Part VIII shall be 
permitted only to apply to those portions of the electrical 
system in the supervised industrial installation used exclu- 
sively for manufacturing or process control activities. 

248.91 Protection of Conductors. Conductors shall be 
protected in accordance with 240.91(A) or (B). 

<Ai CuuTal Conductors shall be protected in accordance 
with 240.4. 

(Bl Devices Rated Over 800 Amperes. Where the over- 
curreni device is rated over 800 an peres die .'jupiciry of 
the conductors it protects shad be equal io oi greatei than 
95 percent oi the rating of ?fac ov< (-current de\ ice ipecified 
in 240.6 in accordance with (Bx I ) and (2i. 

(1) The conductors are protected within recognized time 
vs. cun.-nt limits foi short-circuit currents 

(2) AH equipment in which the conductors umiinate is 
listed and marl ed for the application 

240.92 Location in Circuit. An overcurrent device shall 
be connected in each ungrounded circuit conductor as re- 
quired in 240.92(A) through (E). 

(A) Feeder and Branch-Circuit Conductors. Feeder and 
branch-circuit conductors shall be protected at the point the 
conductors receive their supply as permitted in 240.21 or as 
otherwise permitted in 240.92(B), (C), (D), or (E). 

(B) Feeder Taps. For feeder taps specified in 240.21(B)(2), 
(B)(3), and (B)(4), the tap conductors shall be permitted to be 
sized in accordance with Table 240.92(B). 

(C) Transformer Secondary Conductors of Separately 
Derived Systems. Conductors shall be permitted to be con- 
nected to a transformer secondary of a separately derived sys- 
tem, without overcurrent protection at the connection, where 
the conditions of 240.92(C)(1), (C)(2), and (C)(3) are met. 

(1) Short-Circuit and Ground-Fault Protection. The con- 
ductors shall be protected from short-circuit and ground-fault 
conditions by complying with one of the following conditions: 

(1) The length of the secondary conductors does not ex- 
ceed 30 m (100 ft) and the transformer primary over- 
current device has a rating or setting that does not exceed 
150 percent of the value determined by multiplying the 
secondary conductor ampacity by the secondary-to- 
primary transformer voltage ratio. 

(2) The conductors are protected by a differential relay 
with a trip setting equal to or less than the conductor 
ampacity. 



70-98 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 240 — OVERCURRENT PROTECTION 



240.92 



Table 240.92(B) Tap Conductor Short-Circuit Current 
Ratings. 

Tap conductors are considered to be protected under 
short-circuit conditions when their short-circuit temperature 
limit is not exceeded. Conductor heating under short-circuit 
conditions is determined by (1) or (2): 

(1) Short-Circuit Formula for Copper Conductors 

(I 2 /A 2 )t = 0.0297 log,,, l(T 2 + 234)AT, + 234)] 

(2) Short-Circuit Formula for Aluminum Conductors 

(I 2 IA 2 )t = 0.0125 log,,, [(T, + 228)/(T, + 228)] 

where: 

/ = short-circuit current in amperes 

A = conductor area in circular mils 

t = time of short circuit in seconds (for times less than or equal 
to 10 seconds) 

7, = initial conductor temperature in degrees Celsius. 

T 2 = final conductor temperature in degrees Celsius. 

Copper conductor with paper, rubber, varnished cloth insulation, 

T, = 200 

Copper conductor with thermoplastic insulation, T 2 = 150 

Copper conductor with cross-linked polyethylene insulation, T 2 
= 250 

Copper conductor with ethylene propylene rubber insulation, T 2 
= 250 

Aluminum conductor with paper, rubber, varnished cloth 
insulation, T 2 = 200 

Aluminum conductor with thermoplastic insulation, T 2 - 150 

Aluminum conductor with cross-linked polyethylene insulation, 
T 2 = 250 

Aluminum conductor with ethylene propylene rubber insulation, 
J, = 250 



Informational Note: A differential relay is connected to be 
sensitive only to short-circuit or fault currents within the 
protected zone and is normally set much lower than the 
conductor ampacity. The differential relay is connected to 
trip protective devices that de-energize the protected con- 
ductors if a short-circuit condition occurs. 

(3) The conductors shall be considered to be protected if 
calculations, made under engineering supervision, de- 
termine that the system overcurrent devices will protect 
the conductors within recognized time vs. current limits 
for all short-circuit and ground-fault conditions. 



(2) Overload Protection. The conductors shall be pro- 
tected against overload conditions by complying with 
one of the following: 

(1) The conductors terminate in a single overcurrent device 
that will limit the load to the conductor ampacity. 

(2) The sum of the overcurrent devices at the conductor 
termination limits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses, mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) Overcurrent relaying is connected [with a current trans- 
formers), if needed] to sense all of the secondary con- 
ductor current and limit the load to the conductor am- 
pacity by opening upstream or downstream devices. 

(4) Conductors shall be considered to be protected if cal- 
culations, made under engineering supervision, deter- 
mine that the system overcurrent devices will protect 
the conductors from overload conditions. 

(3) Physical Protection. The secondary conductors are pro- 
tected from physical damage by being enclosed in an ap- 
proved raceway or by other approved means. 

(D) Outside Feeder Taps. Outside conductors shall be per- 
mitted to be tapped to a feeder or to be connected at a trans- 
former secondary, without overcurrent protection at the tap or 
connection, where all the following conditions are met: 

(1) The conductors are protected from physical damage in 
an approved manner. 

(2) The sum of the overcurrent devices at the conductor 
termination limits the load to the conductor ampacity. 
The overcurrent devices shall consist of not more than 
six circuit breakers or sets of fuses mounted in a single 
enclosure, in a group of separate enclosures, or in or on 
a switchboard. There shall be no more than six over- 
current devices grouped in any one location. 

(3) The tap conductors are installed outdoors of a building 
or structure except at the point of load termination. 

(4) The overcurrent device for the conductors is an integral 
part of a disconnecting means or shall be located im- 
mediately adjacent thereto. 

(5) The disconnecting means for the conductors are in- 
stalled at a readily accessible location complying with 
one of the following: 

a. Outside of a building or structure 

b. Inside, nearest the point of entrance of the conductors 

c. Where installed in accordance with 230.6, nearest 
the point of entrance of the conductors 



2011 Edition NATIONAL ELECTRICAL CODE 



70-99 



240.100 



ARTICLE 250 — GROUNDING AND BONDING 



(E) Protection by Primary Overcurrent Device. Con- 
ductors supplied by the secondary side of a transformer 
shall be permitted to be protected by overcurrent protection 
provided on the primary (supply) side of the transformer, 
provided the primary device time-current protection char- 
acteristic, multiplied by the maximum effective primary-to- 
secondary transformer voltage ratio, effectively protects the 
secondary conductors. 

IX. Overcurrent Protection Over 600 Volts, Nominal 
240.100 Feeders and Branch Circuits. 

(A) Location and Type of Protection. Feeder and branch- 
circuit conductors shall have overcurrent protection in each 
ungrounded conductor located at the point where the con- 
ductor receives its supply or at an alternative location in the 
circuit when designed under engineering supervision that 
includes but is not limited to considering the appropriate 
fault studies and time-current coordination analysis of the 
protective devices and the conductor damage curves. The 
overcurrent protection shall be permitted to be provided by 
either 240.100(A)(1) or (A)(2). 

(1) Overcurrent Relays and Current Transformers. Cir- 
cuit breakers used for overcurrent protection of 3-phase 
circuits shall have a minimum of three overcurrent relay 
elements operated from three current transformers. The 
separate overcurrent relay elements (or protective func- 
tions) shall be permitted to be part of a single electronic 
protective relay unit. 

On 3-phase, 3-wire circuits, an overcurrent relay ele- 
ment in the residual circuit of the current transformers shall 
be permitted to replace one of the phase relay elements. 

An overcurrent relay element, operated from a current 
transformer that links all phases of a 3-phase, 3-wire cir- 
cuit, shall be permitted to replace the residual relay element 
and one of the phase-conductor current transformers. 
Where the neutral conductor is not regrounded on the load 
side of the circuit as permitted in 250.184(B), the current 
transformer shall be permitted to link all 3-phase conduc- 
tors and the grounded circuit conductor (neutral). 

(2) Fuses. A fuse shall be connected in series with each 
ungrounded conductor. 

(B) Protective Devices. The protective device(s) shall be 
capable of detecting and interrupting all values of current 
that can occur at their location in excess of their trip-setting 
or melting point. 

(C) Conductor Protection. The operating time of the pro- 
tective device, the available short-circuit current, and the 
conductor used shall be coordinated to prevent damaging or 
dangerous temperatures in conductors or conductor insula- 
tion under short-circuit conditions. 



240.101 Additional Requirements for Feeders. 

(A) Rating or Setting of Overcurrent Protective De- 
vices. The continuous ampere rating of a fuse shall not 
exceed three times the ampacity of the conductors. The 
long-time trip element setting of a breaker or the minimum 
trip setting of an electronically actuated fuse shall not ex- 
ceed six times the ampacity of the conductor. For fire 
pumps, conductors shall be permitted to be protected for 
overcurrent in accordance with 695.4(B;(2). 

(B) Feeder Taps. Conductors tapped to a feeder shall be 
permitted to be protected by the feeder overcurrent device 
where that overcurrent device also protects the tap conductor. 



ARTICLE 250 
Grounding and Howling 

I. General 

250.1 Scope. This article covers general requirements for 
grounding and bonding of electrical installations, and the 
specific requirements in (1) through (6). 

(1) Systems, circuits, and equipment required, permitted, 
or not permitted to be grounded 

(2) Circuit conductor to be grounded on grounded systems 

(3) Location of grounding connections 

(4) Types and sizes of grounding and bonding conductors 
and electrodes 

(5) Methods of grounding and bonding 

(6) Conditions under which guards, isolation, or insulation 
may be substituted for grounding 

Informational Note: See Figure 250.1 for information on 
the organization of Article 250 covering grounding and 
bonding requirements. 

250.2 Definitions. 

Bonding Jumper. Supply-Side. A conductor inslalled on 
the supply skip of a service oi within a service equipment 
enelbsure(s) or { o\ ■■>. separately derived system, that en- 
sures the required electrical conductivity between metal 
parts required to !»..• electricall) connected. 

Effective Ground-Fault Current Path. An intentionally 
constructed, low-impedance electrically conductive path de- 
signed and intended to cany current under ground-fault con- 
ditions from the point of a ground fault on a wiring system to 
the electrical supply source and that facilitates the operation of 
the overcurrent protective device or ground-fault detectors on 
high-impedance grounded systems. 



70-100 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.4 



Part I General 



Part II System 
grounding 



Part VIII Direct-current 
systems 



Part X Grounding of 
systems and circuits of 

1 kV and over (high voltage) 



Part III Grounding electrode 
system and grounding 

electrode conductor 



Part IV Enclosure, 

raceway, and service 

cable grounding 



Part VI Equipment 

grounding and equipment 

grounding conductors 




Part V Bonding 



Part VII Methods of 
equipment grounding 



Part IX Instruments, 
meters, and relays 



Figure 250.1 Grounding and Bonding. 

Ground-Fault Current Path. An electrically conductive 
path from the point of a ground fault on a wiring system 
through normally non-current-carrying conductors, equip- 
ment, or the earth to the electrical supply source. 

Informational Note: Examples of ground-fault current 
paths could consist of any combination of equipment 
grounding conductors, metallic raceways, metallic cable 
sheaths, electrical equipment, and any other electrically 
conductive material such as metal water and gas piping, 
steel framing members, stucco mesh, metal ducting, rein- 
forcing steel, shields of communications cables, and the 
earth itself. 

250.3 Application of Other Articles. For other articles 
applying to particular cases of installation of conductors 
and equipment, grounding and bonding requirements are 
identified in Table 250.3 that are in addition to, or modifi- 
cations of, those of this article. 

250.4 General Requirements for Grounding and Bond- 
ing. The following general requirements identify what 
grounding and bonding of electrical systems are required to 
accomplish. The prescriptive methods contained in Article 
250 shall be followed to comply with the performance re- 
quirements of this section. 



(A) Grounded Systems. 

(1) Electrical System Grounding. Electrical systems that 
are grounded shall be connected to earth in a manner that 
will limit the voltage imposed by lightning, line surges, or 
unintentional contact with higher-voltage lines and that will 
stabilize the voltage to earth during normal operation. 

Informational Note: An important consideration for limit- 
ing the imposed voltage is the routing of bonding and 
grounding electrode conductors so that they are not any 
longer than necessary to complete the connection without 
disturbing the permanent parts of the installation and so 
that unnecessary bends and loops are avoided. 

(2) Grounding of Electrical Equipment. Normally non- 
current-carrying conductive materials enclosing electrical 
conductors or equipment, or forming part of such equip- 
ment, shall be connected to earth so as to limit the voltage 
to ground on these materials. 

(3) Bonding of Electrical Equipment. Normally non- 
current-carrying conductive materials enclosing electrical 
conductors or equipment, or forming part of such equip- 
ment, shall be connected together and to the electrical sup- 
ply source in a manner that establishes an effective ground- 
fault current path. 

(4) Bonding of Electrically Conductive Materials and 
Other Equipment. Normally non-current-carrying electri- 
cally conductive materials that are likely to become ener- 
gized shall be connected together and to the electrical sup- 
ply source in a manner that establishes an effective ground- 
fault current path. 

(5) Effective Ground-Fault Current Path. Electrical equip- 
ment and wiring and other electrically conductive material 
likely to become energized shall be installed in a manner that 
creates a low-impedance circuit facilitating the operation of 
the overcurrent device or ground detector for high-impedance 
grounded systems. It shall be capable of safely carrying the 
maximum ground-fault current likely to be imposed on it from 
any point on the wiring system where a ground fault may 
occur to the electrical supply source. The earth shall not be 
considered as an effective ground-fault current path. 

(B) Ungrounded Systems. 

(1) Grounding Electrical Equipment. Non-current- 
carrying conductive materials enclosing electrical con- 
ductors or equipment, or forming part of such equip- 
ment, shall be connected to earth in a manner that will 
limit the voltage imposed by lightning or unintentional 
contact with higher-voltage lines and limit the voltage to 
ground on these materials. 

(2) Bonding of Electrical Equipment. Non-current-carrying 
conductive materials enclosing electrical conductors or equip- 
ment, or forming part of such equipment, shall be connected 



20U Edition 



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70-101 



250.4 



ARTICLE 250 — GROUNDING AND BONDING 



Table 250.3 Additional Grounding and Bonding Requirements 



Conductor/Equipment 



Article 



Section 



Agricultural buildings 

Audio signal processing, amplification, and 

reproduction equipment 
Branch circuits 
Cablebus 
Cable trays 
Capacitors 
Circuits and equipment operating at less than 50 

volts 
Communications circuits 
Community antenna television and radio distribution 

systems 
Conductors for general wiring 
Cranes and hoists 

Electrically driven or controlled irrigation machines 
Electric signs and outline lighting 
Electrolytic cells 
Elevators, dumbwaiters, escalators, moving walks, 

wheelchair lifts, and stairway chairlifts 
Fixed electric heating equipment for pipelines and 

vessels 
Fixed outdoor electric deicing and snow-melting 

equipment 
Flexible cords and cables 
Floating buildings 
Grounding-type receptacles, adapters, cord 

connectors, and attachment plugs 
Hazardous (classified) locations 
Health care facilities 

Induction and dielectric heating equipment 
Industrial machinery 
Information technology equipment 
Intrinsically safe systems 
Luminaires and lighting equipment 
Luminaires, lampholders, and lamps 
Marinas and boatyards 
Mobile homes and mobile home park 
Motion picture and television studios and similar 

locations 
Motors, motor circuits, and controllers 
Natural and artificially made bodies of water 
Outlet, device, pull, and junction boxes; conduit 

bodies; and fittings 
Over 600 volts, nominal, underground wiring 

methods 
Panelboards 
Pipe organs 

Radio and television equipment 
Receptacles and cord connectors 
Recreational vehicles and recreational vehicle parks 
Services 

Solar photovoltaic systems 

Swimming pools, fountains, and similar installations 
Switchboards and panelboards 
Switches 
Theaters, audience areas of motion picture and 

television studios, and similar locations 
Transformers and transformer vaults 
Use and identification of grounded conductors 
X-ray equipment 



392 
720 
800 



310 
610 

600 

668 
620 



547.9 and 547.10 
640.7 

210.5, 210.6, 406.3 

370.9 

392.60 

460.10, 460.27 



820.93, 820.100, 820.103 
675.11(C), 675.12, 675.13, 675.14, 675.15 

427.29, 427.48 

426.27 

400.22, 400.23 

553.8, 553.10, 553.11 

406.9 



500-517 
517 
665 
670 



410 
550 



430 
682 



645.15 

504.50 

410.40, 410.42, 410.46, 410.155(B) 

555.15 

530.20, 530.64(B) 



682.30, 682.31, 682.32, 682.33 
314.4, 314.25 



650 
810 

551 
230 

680 



200 
660 



300.50(B) 
408.40 

406.3 



690.41, 690.42, 690.43, 690.45, 690.47 

408.3(D) 
404.12 
520.81 

450.10 

517.78 



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NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.20 



together and to the supply system grounded equipment in a 
manner that creates a low-impedance path for ground-fault 
current that is capable of carrying the maximum fault current 
likely to be imposed on it. 

(3) Bonding of Electrically Conductive Materials and 
Other Equipment. Electrically conductive materials that 
are likely to become energized shall be connected together 
and to the supply system grounded equipment in a manner 
that creates a low-impedance path for ground-fault current 
that is capable of carrying the maximum fault current likely 
to be imposed on it. 

(4) Path for Fault Current. Electrical equipment, wiring, 
and other electrically conductive material likely to become 
energized shall be installed in a manner that creates a low- 
impedance circuit from any point on the wiring system to 
the electrical supply source to facilitate the operation of 
overcurrent devices should a second ground fault from a 
different phase occur on the wiring system. The earth shall 
not be considered as an effective fault-current path. 

250.6 Objectionable Current. 

(A) Arrangement to Prevent Objectionable Current. The 

grounding of electrical systems, circuit conductors, surge ar- 
resters, surge-protective devices, and conductive normally 
non-current-carrying metal parts of equipment shall be in- 
stalled and arranged in a manner that will prevent objection- 
able current. 

(B) Alterations to Stop Objectionable Current. If the 

use of multiple grounding connections results in objection- 
able current, one or more of the following alterations shall 
be permitted to be made, provided that the requirements of 
250.4(A)(5) or (B)(4) are met: 

(1) Discontinue one or more but not all of such grounding 
connections. 

(2) Change the locations of the grounding connections. 

(3) Interrupt the continuity of the conductor or conductive 
path causing the objectionable current. 

(4) Take other suitable remedial and approved action. 

(C) Temporary Currents Not Classified as Objection- 
able Currents. Temporary currents resulting from abnormal 
conditions, such as ground faults, shall not be classified as 
objectionable current for the purposes specified in 250.6(A) 
and (B). 

(D) Limitations to Permissible Alterations. The provi- 
sions of this section shall not be considered as permitting 
electronic equipment from being operated on ac systems or 
branch circuits that are not connected to an equipment 
grounding conductor as required by this article. Currents 
that introduce noise or data errors in electronic equipment 



shall not be considered the objectionable currents addressed 
in this section. 

(E) Isolation of Objectionable Direct-Current Ground 
Currents. Where isolation of objectionable dc ground cur- 
rents from cathodic protection systems is required, a listed 
ac coupling/dc isolating device shall be permitted in the 
equipment grounding conductor path to provide an effec- 
tive return path for ac ground-fault current while blocking 
dc current. 

250.8 Connection of Grounding and Bonding Equip- 
ment. 

(A) Permitted Methods. Equipment grounding conduc- 
tors, grounding electrode conductors, and bonding jumpers 
shall be connected by one of the following means: 

(1) Listed pressure connectors 

(2) Terminal bars 

(3) Pressure connectors listed as grounding and bonding 
equipment 

(4) Exothermic welding process 

(5) Machine screw-type fasteners that engage not less than 
two threads or are secured with a nut 

(6) Thread-forming machine screws that engage not less 
than two threads in the enclosure 

(7) Connections that are part of a listed assembly 

(8) Other listed means 

(B) Methods Not Permitted. Connection devices or fittings 
that depend solely on solder shall not be used. 

250.10 Protection of Ground Clamps and Fittings. 

Ground clamps or other fittings shall be approved for gen- 
eral use without protection or shall be protected from 
physical damage as indicated in (1) or (2) as follows: 

(1) In installations where they are not likely to be damaged 

(2) Where enclosed in metal, wood, or equivalent protec- 
tive covering 

250.12 Clean Surfaces. Nonconductive coatings (such as 
paint, lacquer, and enamel) on equipment to be grounded shall 
be removed from threads and other contact surfaces to ensure 
good electrical continuity or be connected by means of fittings 
designed so as to make such removal unnecessary. 

II. System Grounding 

250.20 Alternating-Current Systems to Be Grounded. 

Alternating-current systems shall be grounded as provided for 
in 250.20(A), (B), (C). or (D). Other systems shall be permit- 
ted to be grounded. If such systems are grounded, they shall 
comply with the applicable provisions of this article. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-103 



250.21 



ARTICLE 250 — GROUNDING AND BONDING 



Informational Note: An example of a system permitted to 
be grounded is a corner-grounded delta transformer connec- 
tion. See 250.26(4) for conductor to be grounded. 

(A) Alternating-Current Systems of Less Than 50 Volts. 

Alternating-current systems of less than 50 volts shall be 
grounded under any of the following conditions: 

( 1 ) Where supplied by transformers, if the transformer sup- 
ply system exceeds 150 volts to ground 

(2) Where supplied by transformers, if the transformer sup- 
ply system is ungrounded 

(3) Where installed outside as overhead conductors 

(B) Alternating-Current Systems of 50 Volts to 1000 Volts. 

Alternating-current systems of 50 volts to less than 1000 volts 
that supply premises wiring and premises wiring systems shall 
be grounded under any of the following conditions: 

(1) Where the system can be grounded so that the maxi- 
mum voltage to ground on the ungrounded conductors 
does not exceed 150 volts 

(2) Where the system is 3 -phase, 4- wire, wye connected in 
which the neutral conductor is used as a circuit conductor 

(3) Where the system is 3-phase, 4-wire, delta connected in 
which the midpoint of one phase winding is used as a 
circuit conductor 

(C) Alternating-Current Systems of 1 kV and Over. 

Alternating-current systems supplying mobile or portable 
equipment shall be grounded as specified in 250.188. 
Where supplying other than mobile or portable equipment, 
such systems shall be permitted to be grounded. 

(D) Impedance Grounded Neutral Systems. Impedance 
grounded neutral systems shall be grounded in accordance 
with 250.36 or 250.186. 

250.21 Alternating-Current Systems of 50 Volts to Less 
Than 1000 Volts Not Required to Be Grounded. 

(A) General. The following ac systems of 50 volts to less 
than 1000 volts shall be permitted to be grounded but shall 
not be required to be grounded: 

(1) Electrical systems used exclusively to supply industrial 
electric furnaces for melting, refining, tempering, and 
the like 

(2) Separately derived systems used exclusively for recti- 
fiers that supply only adjustable-speed industrial drives 

(3) Separately derived systems supplied by transformers 
that have a primary voltage rating less than 1000 volts, 
provided that all the following conditions are met: 

a. The system is used exclusively for control circuits. 

b. The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

c. Continuity of control power is required. 



(4) Other systems that are not required to be grounded in 
accordance with the requirements of 250.20(B) 

(B) Ground Detectors. Ground detectors shall be installed 
in accordance; with 250.21(B)(1) and (B)(2). 

(1) Ungrounded alternating current systems as permitted in 
250.21(A)(1) through (A)(4) operating at not less than 
120 volts and not exceeding 1000 volts shall have 
ground detectors installed on the system. 

(2) The ground detection sensing equipment shall be con- 
nected as close a; practicable n, where riic system re- 
vives its simply. 

(C) Marking. Ungrounded systems shall be iec ! bb marked 
■Uni'.'/'it'iUc' System o rfu som e oi first disconnecting 
means oi the system The m ir.Jaf ;h til he of suffii i;nt dura- 
bility U; withstand the environment involved. 

250.22 Circuits Not to Be Grounded. The following cir- 
cuits shall not be grounded: 

(1) Circuits for electric cranes operating over combustible 
fibers in Class III locations, as provided in 503.155 

(2) Circuits in health care facilities as provided in 517.61 
and 517.160 

(3) Circuits for equipment within electrolytic cell working 
zone as provided in Article 668 

(4) Secondary circuits of lighting systems as provided in 
411.5(A) 

(5) Secondary circuits of lighting systems as provided in 
680.23(A)(2). 

250.24 Grounding Service-Supplied Alternating-Current 
Systems. 

(A) System Grounding Connections. A premises wiring 
system supplied by a grounded ac service shall have a 
grounding electrode conductor connected to the grounded 
service conductor, at each service, in accordance with 
250.24(A)(1) through (A)(5). 

(1) General. The grounding electrode conductor connec- 
tion shall be made at any accessible point from the load end 
of the service drop or service lateral to and including the 
terminal or bus to which the grounded service conductor is 
connected at the service disconnecting means. 

Informational Note: See definitions of Service Drop and 
Service Lateral in Article 100. 

(2) Outdoor Transformer. Where the transformer supply- 
ing the service is located outside the building, at least one 
additional grounding connection shall be made from the 
grounded service conductor to a grounding electrode, either 
at the transformer or elsewhere outside the building. 



70-104 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.24 



Exception: The additional grounding electrode conductor 
connection shall not be made on high-impedance grounded 
neutral systems. The system shall meet the requirements of 
250.36. 

(3) Dual-Fed Services. For services that are dual fed 
(double ended) in a common enclosure or grouped together 
in separate enclosures and employing a secondary tie, a 
single grounding electrode conductor connection to the tie 
point of the grounded conductor(s) from each power source 
shall be permitted. 

(4) Main Bonding Jumper as Wire or Busbar. Where the 
main bonding jumper specified in 250.28 is a wire or bus- 
bar and is installed from the grounded conductor terminal 
bar or bus to the equipment grounding terminal bar or bus 
in the service equipment, the grounding electrode conduc- 
tor shall be permitted to be connected to the equipment 
grounding terminal, bar, or bus to which the main bonding 
jumper is connected. 

(5) Load-Side Grounding Connections. A grounded con- 
ductor shall not be connected to normally non-current- 
carrying metal parts of equipment, to equipment grounding 
conductor(s), or be reconnected to ground on the load side 
of the service disconnecting means except as otherwise per- 
mitted in this article. 

Informational Note: See 250.30 for separately derived sys- 
tems, 250.32 for connections at separate buildings or struc- 
tures, and 250. 142 for use of the grounded circuit conduc- 
tor for grounding equipment. 

(B) Main Bonding Jumper. For a grounded system, an un- 
spliced main bonding jumper shall be used to connect the 
equipment grounding conductor(s) and the service-disconnect 
enclosure to the grounded conductor within the enclosure for 
each service disconnect in accordance with 250.28. 

Exception No. 1: Where more than one service disconnect- 
ing means is located in an assembly listed for use as ser- 
vice equipment, an unspliced main bonding jumper shall 
bond the grounded conductor(s) to the assembly enclosure. 

Exception No. 2: Impedance grounded neutral systems 
shall be permitted to be connected as provided in 250.36 
and 250.186. 

(C) Grounded Conductor Brought to Service Equip- 
ment. Where an ac system operating at less than 1000 volts 
is grounded at any point, the grounded conductor(s) shall 
be routed with the ungrounded conductors to each service 
disconnecting means and shall be connected to each discon- 
necting means grounded conductor(s) terminal or bus. A 
main bonding jumper shall connect the grounded conduc- 
tors) to each service disconnecting means enclosure. The 
grounded conductor(s) shall be installed in accordance with 
250.24(C)(1) through (C)(4). 



Exception: Where two or more service disconnecting 
means are located in a single assembly listed for use as 
service equipment, it shall be permitted to connect the 
grounded conductor(s) to the assembly common grounded 
conductor(s) terminal or bus. The assembly shall include a 
main bonding jumper for connecting the grounded conduc- 
tors) to the assembly enclosure. 

(1) Sizing for a Single Raceway. The grounded conductor 
shall not be smaller than the required grounding electrode 
conductor specified in Table 250.66 but shall not be re- 
quired to be larger than the largest ungrounded service- 
entrance conductor(s). In addition, for sets of ungrounded 
service-entrance conductors larger than 1100 kcmil copper 
or 1750 kcmil aluminum, the grounded conductor shall not 
be smaller than 12'/2 percent of the circular mil area of the 
largest set of service-entrance ungrounded conductor(s). 

(2) Parallel Conductors in Two or More Raceways. If 

the ungrounded service-entrance conductors are installed in 
parallel in two or more raceways, the grounded conductor 
shall also be installed in parallel. The size of the grounded 
conductor in each raceway shall be based on the total cir- 
cular mil area of the parallel ungrounded conductors in the 
raceway, as indicated in 250.24(C)(1), but not smaller than 
1/0 AWG. 

Informational Note: See 310.10(H) for grounded conduc- 
tors connected in parallel. 

1 3) Delta- Connected Service. The grounded conductor of 
a 3-phase, 3-wire delta service shall have an ampacity not 
less than that of the ungrounded conductors. 

(4) High Impedance. The grounded conductor on. a high- 
impedance grounded neutral system shall be grounded in 
accordance with 250.36. 

(D) Grounding Electrode Conductor. A grounding elec- 
trode conductor shall be used to connect the equipment 
grounding conductors, the service-equipment enclosures, 
and, where the system is grounded, the grounded service 
conductor to the grounding electrode(s) required by Part III 
of this article. This conductor shall be sized in accordance 
with 250.66. 

High-impedance grounded neutral system connections 
shall be made as covered in 250.36. 

Informational Note: See 250.24(A) for ac system ground- 
ing connections. 

(E) Ungrounded System Grounding Connections. A pre- 
mises wiring system that is supplied by an ac service that is 
ungrounded shall have, at each service, a grounding electrode 
conductor connected to the grounding electrode(s) required by 
Part III of this article. The grounding electrode conductor shall 
be connected to a metal enclosure of the service conductors at 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-105 



250.26 



ARTICLE 250 — GROUNDING AND BONDING 



any accessible point from the load end of the service drop or 
service lateral to the service disconnecting means. 

250.26 Conductor to Be Grounded — Alternating- 
Current Systems. For ac premises wiring systems, the con- 
ductor to be grounded shall be as specified in the following: 

(1) Single-phase, 2-wire — one conductor 

(2) Single-phase, 3-wire — the neutral conductor 

(3) Multiphase systems having one wire common to all 
phases — the common conductor 

(4) Multiphase systems where one phase is grounded — 
one phase conductor 

(5) Multiphase systems in which one phase is used as in 
(2) — the neutral conductor 

250.28 Main Bonding Jumper and System Bonding 
Jumper. For a grounded system, main bonding jumpers 
and system bonding jumpers shall be installed as follows: 

(A) Material. Main bonding jumpers and system bonding 
jumpers shall be of copper or other corrosion-resistant mate- 
rial. A main bonding jumper and a system bonding jumper 
shall be a wire, bus, screw, or similar suitable conductor. 

(B) Construction. Where a main bonding jumper or a sys- 
tem bonding jumper is a screw only, the screw shall be 
identified with a green finish that shall be visible with the 
screw installed. 

(C) Attachment. Main bonding jumpers and system bond- 
ing jumpers shall be connected in the manner specified by 
the applicable provisions of 250.8. 

(D) Size. Main bonding jumpers and system bonding 
jumpers shall be sized in accordance with 250.28(D)(1) 
through (D)(3). 

(1) General. Main bonding jumpers and system bonding 
jumpers shall not be smaller than the sizes shown in 
Table 250.66. Where the supply conductors are larger 
than 1100 kcmil copper or 1750 kcmil aluminum, the 
bonding jumper shall have an area that is not less than 
12'/2 percent of the area of the largest phase conductor 
except that, where the phase conductors and the bonding 
jumper are of different materials (copper or aluminum), 
the minimum size of the bonding jumper shall be based 
on the assumed use of phase conductors of the same 
material as the bonding jumper and with an ampacity 
equivalent to that of the installed phase conductors. 

(2) Main Bonding Jumper for Service with More Than 
One Enclosure. Where a service consists of more than a 
single enclosure as permitted in 230.71(A), the main bond- 
ing jumper for each enclosure shall be sized in accordance 



with 250.28(D)(1) based on the largest ungrounded service 
conductor serving that enclosure. 

(3) Separately Derived System with More Than One 
Enclosure. Where a separately derived system supplies 
more than a single enclosure, the system bonding jumper 
for each enclosure shall be sized in accordance with 
250.28(D)(1) based on the largest ungrounded feeder con- 
ductor serving that enclosure, or a single system bonding 
jumper shall be installed at the source and sized in accor- 
dance with 250.28(D)(1) based on the equivalent size of the 
largest supply conductor determined by the largest sum of 
the areas of the corresponding conductors of each set. 

250.30 Grounding Separately Derived Alternating- 
Current Systems. In addition to complying with 250.30(A) 
for grounded systems, or as provided in 250.30(B) for un- 
grounded systems, separately derived systems shall comply 
with 250.20, 250.21,250.22, and 250.26. 

Informational Note No. I: An alternate ac power source, 
sue! as an on-sit£ generator is rot a sepai ttelj derived 

; t> m u the grpi tided v ,i.idn toi is -on lly info rconnei ed 
to a service ,nn|u-d system grounded conductoi \n ex- 

imple > " I. i ituation i: he ilternate source ti i in 
equipment tine-, not include a ' witching action m the grounded 
conduc'oi and allows il t i remain solidly connected to the 
service-supplied grounded conducioi when ihe alternate 
soutcc is operational and supplying fije load served. 

Informational Note No. 2: See 445.13 for the minimum 
size of < onductoi > fh <i earrj fault current. 

(A) Grounded Systems. A separately derived ac system that 
is grounded shall comply with 250.30(A)(1) through (A)(8). 
Except as otherwise permitted in this article, a grounded con- 
ductor shall not be connected to normally non-current- 
carrying metal parts of equipment, be connected to equipment 
grounding conductors, or be reconnected to ground on the 
load side of the system bonding jumper. 

Informational Note: See 250.32 for connections at sepa- 
rate buildings or structures, and 250.142 for use of the 
grounded circuit conductor for grounding equipment. 

Exception: Impedance grounded neutral system grounding 
connections shall be made as specified in 250.36 or 
2.*/'. 1,\6. ti.\ applicable. 

(1) System Bonding Jumper. An unspliced system bond- 
ing jumper shall comply with 250.28(A) through (D). This 
connection shall be made at any single point on the sepa- 
rately derived system from the source to the first system 
disconnecting means or overcurrent device, or it shall be 
made at the source of a separately derived system that has 
no disconnecting means or overcurrent devices, in accor- 
dance with 250.30(A)(1)(a) or (b): The system bonding 
jumper shall remain within the enclosure Where it brigi- 



70-106 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.30 



,1 ites It tii"; mhiko i ; !<>' ated ->mi side in.- ')i>ilili.,c oi stru 
ture supplied, i system bonding ni'iijia shall be installed al 
the grounding electrode connection in compliance with 
250.30(C). 

Exception No. 1: For systems installed in accordance with 
450.6, a single system bonding jumper connection to the tie 
point of the grounded circuit conductors from each power 
source shall be permitted. 

Exception No. 2: A system bonding jumper at both the 
source and the first disconnecting means shall be permitted 
if doing so does not establish a parallel path for the 
grounded conductor. If a grounded conductor is used in this 
manner, it shall not be smaller than the size specified for 
the system bonding jumper but shall not be required to be 
larger than the ungrounded conductors). For the purposes 
of this exception, connection through the earth shall not be 
considered as providing a parallel path. 
Exception No. 3: The size of the system bonding jumper 
for a system that supplies a Class 1, Class 2, or Class 3 
circuit, and is derived from a transformer rated not more 
than 1000 volt-amperes, shall not be smaller than the de- 
rived ungrounded conductors and shall not be smaller than 
14 AWG copper or 12 AWG aluminum. 

(a) Installed at the Source. The ;ystem bonding jump*-* 
sh ill connect uV grounded conductor to '/«* supply-side card- 
ing jnnithT and Jc n >>i\nl'y nonn urrent ca r ng metal in- 
cisure. 

(b) Installed at die First Disconnecting Means, ihc 
system bonding )» mp :i shall conned the groin sLri conducioi 
to the i'ipt»]\ side hwidint jii nper, tin disconnecting men 
enclosure, and the equipment grounding conductors)". 

(2) Supply-Side Bonding Jumper, il tin ;un of; »cpi 

rately derived sj u in ..nd tin i im diM-ctui.. tsvz m?an; m 
located in separate enclosures, a supply-sidf bonding 
jumper shall be installed with the circuit conductors iwm 
the source enclosure to the fir.t disconnecting means. A 
'.< [ipl- rid bci'd.r,.; ,tini<i i villi not U required to rv 
larger than the lerived ungrounded conductor! i'iic ap;l"- 
i l( uOiidi!^ !■ mpei h ill ! -i- pc nitted n* b- oi n ,.ii|j;jl.<-> 
metal raceway t; pe or of die wire or bus type as lotions 

(a) A supply-side bonding jumper of the wife type 
shall comply with 250. 1 02(C), based on the size of the 
derived ungro mded conductors. 

(b) A iitpph itic bonding jumper ol the bw type shall 
have a cross-sectional area nol smaller than a supply-side 
bc.iJi.it! ifni^ti el tlu hi,c ; pen ntvwci'-nw 50 '()'(''• 

(3) Grounded Conductor, if a grounded conductoi i: in- 
stalled and the system bonding juniper connection is no! 
located at the source, 250.30(A)(3)(a) through (A)(3)(d) 
shall apply. 

(a) Sizing , >• • >i i J *? cew ty l|i<- ^r")«,hi-i 'in 
ductor shall not be smaller than the required grounding 



electrode < onductor specified in Table 250.66 but shall not 
be required to he lair/f l than the largest derived unj rounded 
coriductor(.s) In addition, foi sets <<1 duned iiris' ouiif I "•■ 1 
'„oi»fi.U'<i. la.-gtr than 1I(J0 land « oppei or 1 7" r >0 kemil 
aluminum, the grounded conductor shall not be smaller 
than 12 <•■ percenl o< the circular mil area of the largest set 
of derivi d ungrounded conductors. 

(b) Parallel Conductors in Two or Mart F,'h\\vays. If 
the ungrounded conductors an nvi -ll> c! m paralli ! in two 
or more raceways, the grounded conductor -.hal! also be 
installed in jaralleL J he size of the gro uHeJ condui tor in 
each raceway shall be based on lite total circular mil area of 
the p.i'aPei derived ungrounded conductoi in the i.n ;wa> as 
indicated in 250. : i0(A)(3)(a), but not smaller than 1/0 AWG. 

Informational Note: See 310.10(H) for grounded conduc- 
tors connected ip parallel 

(c) Del>. r : Connected System. The grounded conductor 
of a 3-phase, 3-wire delta system shall have an ampacity 
mt 1 . , "i't'-t.iai '1 '^ uni.K<iti! 'e1 ' onductois. 

(d) Impedance Grounded System. The grounded con- 
ductor of an impedance grounded ncn.ra] system shall be in- 
tailed in a< oid^h.i \,it| ( 1J: 56 o. '~>0 1S6 ,i>- applicable 

(4) Groniibing F.Jectrode. The grounding electrode shall 
be as near as practicable to, and preferably in the same area 
as. the grounding electrode conductor connection to the 
- ) stem The grounding electrode shall be the nearest of one 
of the following: 

(1) Mela I watei pipe grounding electrode as specified in 
250.52(A)(1) 

(2) Structural metal grounding electrode as specified in 
250.52(A)(2) 

t\ eption No : Am oj the >ther elet rodes identified in 
250.52(A) shall h used ij ilu electrodes pecified by 
250.30(A)(4) are not available. 

Exception No. 2 to (1) and (2): If a separately derived 
;ystei originatt v i,, listi '• equipment \"iini>!" foi n e "\ 
service equipment the grounding electrode used for tin 
si rvice or feeder equipment shall be permitted as the 
grounding electrode for the separately derived system. 

Informational Note No. I: See 250.104(D) for bonding 
requirements foi iiu-moi metal watei piping in the area 
served by ieparatel\ derived systems. 

Informational Note No. 2: See 250.50 and 250.58 for re- 
quirements foi bonding ill electrodes together if located at 
the same building oi structure. 

(5) Grounding Electrode Conductor, Single Separately 
Derived System. A grounding electrode conductor for a 
single separately derived system shall be sized in accor- 
dance with 250.66 for the derived ungrounded conductors* 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-107 



250.30 



ARTICLE 250 — GROUNDING AND BONDING 



Ti shall be used to connect the grounded conductor of the 
derived system to the grounding electrode as specified in 
250.30(A)(4). This connection shall be made at the same 
point on the separately derived system where the system 
bonding jumper is connected. 

Exception No. 1 : If the system bonding jumper specified in 
250.30(A)(1) is a wire or busbar, it shall be permitted to 
connect the grounding electrode conductor to the equip- 
ment grounding terminal, bar, or bus, provided the equip- 
ment grounding terminal, bar, or bus is of sufficient size for 
the separately derived system. 

Exception No. 2: If a separately derived system originates 
in listed equipment suitable as service equipment, the 
grounding electrode conductor from the service or feeder 
equipment to the grounding electrode shall be permitted as 
the grounding electrode conductor for the separately de- 
rived system, provided the grounding electrode conductor is 
of sufficient size for the separately derived system. If the 
equipment grounding bus internal to the equipment is not 
smaller than the required grounding electrode conductor 
for the separately derived system, the grounding electrode 
connection for the separately derived system shall be per- 
mitted to be made to the bus. 

Exception No. 3: A grounding electrode conductor shall 
not be required for a system that supplies a Class I, Class 
2, or Class 3 circuit and is derived from a transformer 
rated not more than 1000 volt-amperes, provided the 
grounded conductor is bonded to the transformer frame or 
enclosure by a jumper sized in accordance with 250.30(A)(1), 
Exception No. 3, and the transformer frame or enclosure is 
grounded by one of the means specified in 250.134. 

(6) Grounding Electrode Conductor, Multiple Sepa- 
rately Derived Systems. A common grounding electrode 
conductor for multiple separately derived systems shall be 
permitted ii installed the common grounding electrode 
conductor shall be used to connect the grounded conductor 
of the separately derived systems to the grounding elcc- 
trode « . ,}t.vitu-i! ,n 250 Uh \ K-li. \ grounding electrod 
conductor tap shall then be installed from each separately 
derived system to the common grounding electrode eon- 
.Ui'.tui E ii.h tap ■ ondui toi li.ill c onnect the grounded con 
ductor of the separately lerived system to th< lommon 
grounding electrode conductor. This connection shall be 
made at the same point on the .separately derived system 
where the system bonding jumper is connected. 
Exception No. 1: If the system bonding jumper specified in 
250.30(A)(1) is a wire or busbar, it shall be permitted, to 
connect the grounding electrode conductor tap to the 
equipment grounding terminal, bar, or bus, provided the 
equipment grounding terminal, bar, or bus is of sufficient 
size for the separately derived system. 

Exception No. 2: A grounding electrode conductor shall not 
be required for a system that supplies a Class 1, Class 2, or 



Class 3 circuit and is derived from a transformer rated not 
more than 1000 volt-amperes, provided the system grounded 
conductor is bonded to the transformer frame or enclosure by 
a jumper sized in accordance with 250.30(A)(1), Exception 
No. 3, and the transformer frame or enclosure is grounded by 
one of the means specified in 250.134. 

(a) Common Grounding Electrode Conductor. The 
common grounding electrode conductor shall be permitted 
to be one ol the follow ing: 

(1) Aconductoi of the w ire type not smaller than 3/0 AWG 
copper or 250 kemil aluminum 

(2) The metal frame of the building or structure that com- 
plies with I5i) 52(A i.2t i« h conn ; :ted to the ground- 
ing ekutode system by t conductor uW hjiil not be 
smaller man 3/0 AWG copper or 250 kemil aluminum 

(b) Tap Conductor Size. Each tap conductor shall be 
sized in accordance with 250.66 based on the derived un- 
grounded conductors of the separately derived system it 
serves. 

Exception: If a separately derived system originates in 
listed equipment suitable as service equipment, the ground- 
ing electrode conductor from the sendee or feeder equip- 
ment to the grounding electrode shall be permitted as the 
grounding electrode conductor for the separately derived 
system, provided the grounding electrode conductor is of 
sufficient size for the separately derived system. If the 
equipment ground, bus internal to the equipment is not 
smaller than the required grounding electrode conductor 
for the separately derived, system, the grounding electrode 
connection for the separately derived system shall be per- 
mitted to be made to the bus. 

(c) Connections. All tap connections to the common 
grounding electrode conductor shall be made at an acces- 
sible location by one of the following methods: 

(1) A connector listed i grounding ind bonding equipment. 

(2) Listed connections to aluminum or copper busbars not 
smaller than 6 mm x 50 mm ('A in. x 2 in.). If alumi- 
num busbars are used, the installation shall comply 
with 250.64(A). 

(3) The exothermic welding process. 

Tap conductors shall be connected to the common ground- 
ing electrode conductor in such a manner that the common 
grounding electrode conductor remains without a splice or 
joint. 

(7) Installation. The installation of all grounding electrode 
conductors shall comply with 250.64(A), (B), (C), and (E). 

(8) Bonding. Structural steel and metal piping shall be 
connected to the grounded conductor of a separately de- 
rived system in accordance with 250.104(D). 



70-108 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.32 



(B) Ungrounded Systems. The equipment of an un- 
grounded separately derived system shall be grounded and 

bonded as specified in 250.30(B)(1) through (B)(3). 

(1) Grounding Electrode Conductor. A grounding elec- 
trode conductor, sized in accordance with 250.66 for the 

largest derived ungrounded conductor (s) or set of derived 
ungrounded conductors, shall be used to connect the metal 
enclosures of the derived system to the grounding electrode 
as specified in 250.30(A)(5) or (6), as applicable. This con- 
nection shall be made at any point on the separately derived 
system from the source to the first system disconnecting 
means. If tht source is located .'uImJc the b.iiM'4". m ^tpu 
ture supplied, a grounding electrode connection <-hall be 
madi in compliance with 250.30(C). 

(2) Grounding Electrode. Except as permitted by 250.34 
for portable and vehicle-mounted generators, the grounding 
electrode shall comply with 250.30(A)(4). 

(3) Bonding Path and Conductor. A supp >id bond • ■_. 
jumper shall be installed >m>,i th< source ••! a separately 
derived system to the first disconnecting m :ans in compli- 
ance with 250.30(A)(2). 

(C) Outdoor Source. If the source of the separate!) de 
rived system is located outside the building of structure 
supplied, a grounding electrode connmrioi. sh'il! be made at 
the source location to one or more grounding electrode; in 
compliance v,Jh !50 -0 hi ad iiii"i>» ihr installation 4,c,;l 
comply with 250.30(A) for grounded systems or with 
250.3()(B> foi ungrounded -\ stems. 

Exception: The grounding electn de rihun, tot . mnecti m 
for impedance grounded neutral systems shall imply \ ith 
250.36 or 250.186, as applicable. 

250.32 Buildings or Structures Supplied by a Feeder(s) 
or Branch Circuit(s). 

(A) Grounding Electrode. Building(s) or structure(s) sup- 
plied by feeder(s) or branch circuit(s) shall have a ground- 
ing electrode or grounding electrode system installed in 
accordance with Part III of Article 250. The grounding 
electrode conductor(s) shall be connected in accordance 
with 250.32(B) or (C). Where there is no existing ground- 
ing electrode, the grounding electrode(s) required in 250.50 
shall be installed. 

Exception: A grounding electrode shall not be required 
where only a single branch circuit, including a multiwire 
branch circuit, supplies the building or structure and the 
branch circuit includes an equipment grounding conductor 
for grounding the normally non-current-carrying metal 
parts of equipment. 



(B) Grounded Systems. 

(!) Supplied h< :< Kraler or Branch Circuit. An equip- 
ment grounding conductor, as described in 250.118, shall 
be run with the supply conductors and be connected to the 
building or structure disconnecting means and to the 
grounding electrode(s). The equipment grounding conduc- 
tor shall be used for grounding or bonding of equipment, 
structures, or frames required to be grounded or bonded. 
The equipment grounding conductor shall be sized in ac- 
cordance with 250.122. Any installed grounded conductor 
shall not be connected to the equipment grounding conduc- 
tor or to the grounding electrode(s). 

Exception: For installations made in compliant < i. ith pre- 
viou e Mom oj <h,\ ( ode that j ermitted such connection, 
the grounded conductor run with the supply to the building 
or structure shall be permitted to teive as the ground-fault 
return path ij all of Hit following requirements continue to 
be met: 

(1) An equipment grounding conductor is not run with the 
supply to the building or structure. 

(2) There are no continuous metallic paths bonded to the 
grounding system in each building or structure involved. 

(3) Ground-fault protection of equipment has not been in- 
stalled on the supply side of the feeder(s). 

If the grounded conductor is used for grounding in accor- 
dance with the provision of this exception, the size of the 
grounded conductor shall not be smaller than the larger of 
either of the following: 

(1) That required by 220.61 

(2) That required by 250.122 

(2) Supplied b} Separately Derived System. 

(a) With Ovt rcurreni Protection. 11 uvercurrent protec- 
tion .. provided when the < onductoi > < riginate, the instal- 
lation shall comply with 250.32(B)(1). 

(b) fy>;iiuiii Oyercurreni Protection. [I over/current 
protection is no! provided where the conductors originate. 
the installation shall comply with 250.30(A). If installed, 
the supply-side bonding jumper shall be connected to the 
building or structure disconnecting means and to the 
grounding tkt trode(s). 

(C) Ungrounded Systems. 

(1) Supplied by a J xr.-der or Branch Circuit. An equip- 
ment grounding conductor, as described in 250.118, shall 
be installed with the supply conductors and be connected to 
rlr building or structure disconnecting mcaii t'u to the 
{ ioi'wIi, a electrode! * " he grounding < ' :c rode( ) sh; I' also 
be eonnectet to the building oi structure dis orin cting means. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-109 



250.34 



ARTICLE 250 — GROUNDING AND BONDING 



(2) Supplied In a Separately Derived System. 

(a) With Overcurrent Protection. If overcurrent protec- 
tion is provided <Aii< re d>: i ondu< tors originate, the inst <i- 
lation shall comply with (C)(1). 

(b) Without "Overcurrent Protection: If overcurxelll 
protection is not m.» ><|,-.i where -lie conductors originate 
the installation shall cornpb with 250.30(B) If installed 
the supply-side b« nding iui«}>f< shall be connected It, the 
building or true tun disconnecting means -I'M to the 
grounding electrode(s). 

(D) Disconnecting Means Located in Separate Building 
or Structure on the Same Premises. Where one or more 
disconnecting means supply one or more additional buildings 
or structures under single management, and where these dis- 
connecting means are located remote from those buildings or 
structures in accordance with the provisions of 225.32, Excep- 
tion No. 1 and No. 2, 700.12(B)(6), 701.12(B)(5), or 702.12, 
all of the following conditions shall be met: 

(1) The connection of the grounded conductor to the 
grounding electrode, to normally non-current-carrying 
metal parts of equipment, or to the equipment ground- 
ing conductor at a separate building or structure shall 
not be made. 

(2) An equipment grounding conductor for grounding and 
bonding any normally non-current-carrying metal parts 
of equipment, interior metal piping systems, and build- 
ing or structural metal frames is run with the circuit 
conductors to a separate building or structure and con- 
nected to existing grounding electrode(s) required in 
Part III of this article, or, where there are no existing 
electrodes, the grounding electrode(s) required in Part 
III of this article shall be installed where a separate 
building or structure is supplied by more than one 
branch circuit. 

(3) The connection between the equipment grounding con- 
ductor and the grounding electrode at a separate build- 
ing or structure shall be made in a junction box, panel- 
board, or similar enclosure located immediately inside 
or outside the separate building or structure. 

(E) Grounding Electrode Conductor. The size of the 
grounding electrode conductor to the grounding elec- 
trode^) shall not be smaller than given in 250.66, based on 
the largest ungrounded supply conductor. The installation 
shall comply with Part III of this article. 

250.34 Portable and Vehicle-Mounted Generators. 

(A) Portable Generators. The frame of a portable genera- 
tor shall not be required to be connected to a grounding 
electrode as defined in 250.52 for a system supplied by the 
generator under the following conditions: 



(1) The generator supplies only equipment mounted on the 
generator, cord-and-plug-connected equipment through 
receptacles mounted on the generator, or both, and 

(2) The normally non-current-carrying metal parts of equip- 
ment and the equipment grounding conductor terminals of 
the receptacles are connected to the generator frame. 

(B) Vehicle-Mounted Generators. The frame of a vehicle 
shall not be required to be connected to a grounding electrode 
as defined in 250.52 for a system supplied by a generator 
located on this vehicle under the following conditions: 

(1) The frame of the generator is bonded to the vehicle 
frame, and 

(2) The generator supplies only equipment located on the 
vehicle or cord-and-plug-connected equipment through 
receptacles mounted on the vehicle, or both equipment 
located on the vehicle and cord-and-plug-connected 
equipment through receptacles mounted on the vehicle 
or on the generator, and 

(3) The normally non-current-carrying metal parts of equip- 
ment and the equipment grounding conductor terminals of 
the receptacles are connected to the generator frame. 

(C) Grounded Conductor Bonding. A system conductor 
that is required to be grounded by 250.26 shall be con- 
nected to the generator frame where the generator is a com- 
ponent of a separately derived system. 

Informational Note: For grounding portable generators 
supplying fixed wiring systems, see 250.30. 

250.35 Permanently Installed Generators. A conductor 
that provides an effective ground-fault current path shall be 
installed with the supply conductors from a permanently 
installed generator(s) to the first disconnecting mean(s) in 
accordance with (A) or (B). 

(A) Separately Derived System. If the generator is in- 
stalled as a separately derived system, the requirements in 
250.30 shall apply. 

(B) Nonseparately Derived System. Tf the generator is in- 
stalled as a nonseparatel} derived system, and overcurrent 
iioiuuoi, •'. not integral with the generate! assembly; a 
supply-side N.rdiii'j .' mpei hall be installed between ili<_- 
generator juhji.ihuT grouridihg terminal >t<<i the equipmenl 
sjuo'nijiuj. terminal, I ar, or b ^ oi the di jconni i »>m meati(s) 
«» shall be sized in accordance with 250 102(C) based on the 
size of the conductors supplied by the generator. 

250.36 High-Impedance Grounded Neutral Systems. 

High-impedance grounded neutral systems in which a 
grounding impedance, usually a resistor, limits the ground- 
fault current to a low value shall be permitted for 3-phase 
ac systems of 480 volts to 1000 volts if all the following 
conditions are met: 



70-110 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.52 



(1) The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

(2) Ground detectors are installed on the system. 

(3) Line-to-neutral loads are not served. 

High-impedance grounded neutral systems shall com- 
ply with the provisions of 250.36(A) through (G). 

(A) Grounding Impedance Location. The grounding im- 
pedance shall be installed between the grounding electrode 
conductor and the system neutral point. If a neutral point is 
not available, the grounding impedance shall be installed 
between the grounding electrode conductor and the neutral 
point derived from a grounding transformer. 

(B) Grounded System Conductor. The grounded system 
conductor from the neutral point of the transformer or gen- 
erator to its connection point to the grounding impedance 
shall be fully insulated. 

The grounded system conductor shall have an ampacity 
of not less than the maximum current rating of the ground- 
ing impedance but in no case shall the grounded system 
conductor be smaller than 8 AWG copper or 6 AWG alu- 
minum or copper-clad aluminum. 

(C) System Grounding Connection. The system shall 
not be connected to ground except through the grounding 
impedance. 

Informational Note: The impedance is normally selected 
to limit the ground-fault current to a value slightly greater 
than or equal to the capacitive charging current of the sys- 
tem. This value of impedance will also limit transient ov- 
ervoltages to safe values. For guidance, refer to criteria for 
limiting transient overvoltages in ANSI/IEEE 142-1991, 
Recommended Practice for Grounding of Industrial and 
Commercial Power Systems. 

(D) Neutral Point to Grounding Impedance Conductor 
Routing. The conductor connecting the neutral point of the 
transformer or generator to the grounding impedance shall 
be permitted to be installed in a separate raceway from the 
ungrounded conductors. It shall not be required to run this 
conductor with the phase conductors to the first system 
disconnecting means or overcurrent device. 

(E) Equipment Bonding Jumper. The equipment bond- 
ing jumper (the connection between the equipment ground- 
ing conductors and the grounding impedance) shall be an 
unspliced conductor run from the first system disconnecting 
means or overcurrent device to the grounded side of the 
grounding impedance. 

(F) Grounding Electrode Conductor Location. The 

grounding electrode conductor shall be connected at any 
point from the grounded side of the grounding imped- 
ance to the equipment grounding connection at the ser- 
vice equipment or first system disconnecting means. 



(G) Equipment Bonding Jumper Size. The equipment 
bonding jumper shall be sized in accordance with (1) or (2) 
as follows: 

(1) If the grounding electrode conductor connection is 
made at the grounding impedance, the equipment 
bonding jumper shall be sized in accordance with 
250.66, based on the size of the service entrance 
conductors for a service or the derived phase con- 
ductors for a separately derived system. 

(2) If the grounding electrode conductor is connected at the 
first system disconnecting means or overcurrent device, 
the equipment bonding jumper shall be sized the same 
as the neutral conductor in 250.36(B). 

III. Grounding Electrode System and Grounding 
Electrode Conductor 

250.50 Grounding Electrode System. All grounding elec- 
trodes as described in 250.52(A)(1) through (A)(7) that are 
present at each building or structure served shall be bonded 
together to form the grounding electrode system. Where 
none of these grounding electrodes exist, one or more of 
the grounding electrodes specified in 250.52(A)(4) through 
(A)(8) shall be installed and used. 

Exception: Concrete-encased electrodes of existing build- 
ings or structures shall not be required to be part of the 
grounding electrode system where the steel reinforcing bars 
or rods are not accessible for use without disturbing the 
concrete. 

250.52 Grounding Electrodes. 

(A) Electrodes Permitted for Grounding. 

(1) Metal Underground Water Pipe. A metal underground 
water pipe in direct contact with the earth for 3.0 m (10 ft) or 
more (including any metal well casing bonded to the pipe) and 
electrically continuous (or made electrically continuous by 
bonding around insulating joints or insulating pipe) to the 
points of connection of the grounding electrode conductor and 
the bonding conductor! s) or jumper(s), if installed. 

(2) Metal Frame of the Building or Structure. The metal 
frame of the building or structure that is connected to the 
earth by one or more of the following methods: 

(1) At least one structural metal member that is in direct 
contact with the earth for 3.0 m ( 10 ft) or more, with or 
without concrete encasement. 

(2) Hold-down bolts securing the structural steel column 
that are connected to a concrete-encased electrode that 
complies with 250.52(A)(3) and is located in the sup- 
port footing or foundation. The hold-down bolls shall 
be connected to the concrete-encased electrode by 
welding, exothermic welding, the usual steel tie wires, 
or other approved means. 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-111 



250.53 



ARTICLE 250 — GROUNDING AND BONDING 



(3) Concrete-Encased Electrode. A concrete-encased 
electrode shall consist of at least 6.0 m (20 ft) of either 
(1) or (2): 

(1) One or more bare or zinc galvanized or oilier electri- 
cally c(r.ih%nve coated steel reinforcing bars or rods of 
not less than 13 mm (Vi in.) in diameter, installed in 
one continuous 6.0 m. (20 ft) length, or if in multiple 
pieces connected together by thv usual steel rie wires, 
>"--ii,iMui welding welding, oi rther e eUi\> means 
to create a 6.0 m (20 ft) or greater length; or 

(2) Bare copper conductor not smaller than 4 AWG 

Metallic components shall be encased by at least 
.50 mm (2 in.) of concrete and shall be located hori- 
zontally within that portion of a concrete foundation 
or footing that is in direct contact with the earth or 
within vertical foundations or structural components 
or members that are in direct contact with the earth. 
If multiple concrete-encase I t le trodes ire present at 
a building or structure, it shallbe permissible to bond 
only one into the grounding electrode system. 

Informational Note: i ohefeti install ih, thinsii ii.on • i 
por barriers, films or similai items separating the concrete 
from the earth is not considered to he in "direct contact" 
with the earth. 

(4) Ground Ring. A ground ring encircling the building or 
structure, in direct contact with the earth, consisting of at 
least 6.0 m (20 ft) of bare copper conductor not smaller 
than 2 AWG. 

(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall 
not be less than 2.44 m (8 ft) in length and shall consist of the 
following materials. 

(a) Grounding electrodes of pipe or conduit shall not be 
smaller than metric designator 21 (trade size %) and, where of 
steel, shall have the outer surface galvanized or otherwise 
metal-coated for corrosion protection. 

(b) Rod-type grounding electrodes of stainless steel 
and copper or zinc coated steel shall be at least 15.87 mm 
( 5 /8 in.) in diameter, unless listed. 

(6) Other Listed Electrodes. Other listed grounding elec- 
trodes shall be permitted. 

(7) Plate Electrodes. Each plate electrode shall expose not 
less than 0.186 m 2 (2 ft 2 ) of surface to exterior soil. Elec- 
trodes of bare or conductively coated iron or steel plates 
shall be at least 6.4 mm ('A in.) in thickness. Solid, uncoated 
electrodes of nonferrous metal shall be at least 1.5 mm 
(0.06 in.) in thickness. 

(8) Other Local Metal Underground Systems or Struc- 
tures. Other local metal underground systems or structures 
such as piping systems, underground tanks, and under- 
ground metal well casings that are not bonded to a metal 
water pipe. 



(B) Not Permitted for Use as Grounding Electrodes. 

The following systems and materials shall not be used as 
grounding electrodes: 

(1) Metal underground gas piping systems 

(2) Aluminum 

Informational Note: See 250.104(B) for bonding require- 
ments of gas piping. 

250.53 Grounding Electrode System Installation. 

Informational Note: See 547.9 and 547.10 for special 
grounding and bonding requirements for agricultural 
buildings. 

(A) Rod, Pipe, and Plate Electrodes. Rod, pipe, and plate 
electrodes shall meet the requirements of 250.53(A)(1) 
through (A)(3). 

(1) Below Permanent Moisture Level. If practicable, rod, 
pipe, and plate electrodes shall be embedded below perma- 
nent moisture level. Rod, pipe, and plate electrodes shall be 
free from nonconductive coatings such as paint or enamel. 

(2) Supplemental Electrode Required. A single rod. pipe, 
or plate electrode skill !.><■■ supplemented by an additional 
electrode of a type specified in 250.52(A)(2) through 
(A)(8). The stippkmeiital electrode shall be permitted to be 
bonded to one of the following: 

(1) Rod. pipe, or plate electrode 

(2) Grounding electrode conductor 

(3) Gr> Hided sen ce-entrana conductor 

(4) Nonflexible fo-iud^i service i leeway 

(5) Any grounded service enclosure 

Exception: If a i qle ■ >d ripe, oi ph te grounding elec- 
trode has a resistance to earth of "'3 ohms or less, the 
supplemental -let rode shall not be required. 

(3) Supplemental Elect ode. If multiple rod. pipe, or plate 

electrodes are installed to in.vi the requirements of this 
section, they shall not be less than 1.8 m (6 ft) apart. 

Informational Note: The paralleling efficiency of rods is 
in'crea ed by spacing them tv ice the length oi the longest rod 

(B) Electrode Spacing. Where more than one of the elec- 
trodes of the type specified in 250.52(A)(5) or (A)(7) are 
used, each electrode of one grounding system (including 
that used for strike termination devices) shall not be less 
than 1.83 m (6 ft) from any other electrode of another 
grounding system. Two or more grounding electrodes that 
are bonded together shall be considered a single grounding 
electrode system. 

(C) Bonding Jumper. The bonding jumper(s) used to con- 
nect the grounding electrodes together to form the ground- 
ing electrode system shall be installed in accordance with 



70-112 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.64 



250.64(A), (B), and (E), shall be sized in accordance with 
250.66, and shall be connected in the manner specified in 
250.70. 

(D) Metal Underground Water Pipe. If used as a ground- 
ing electrode, metal underground water pipe shall meet the 
requirements of 250.53(D)(1) and (D)(2). 

(1) Continuity. Continuity of the grounding path or the 
bonding connection to interior piping shall not rely on wa- 
ter meters or filtering devices and similar equipment. 

(2) Supplemental Electrode Required. A metal under- 
ground water pipe shall be supplemented by an additional 
electrode of a type specified in 250.52(A)(2) through 
(A)(8). If the supplemental electrode is of the rod, pipe, or 
plate type, it shall comply with 250.53(A). The supplemen- 
tal electrode shall be bonded to one of the following: 

(1) Grounding electrode conductor 

(2) Grounded service-entrance conductor 

(3) Nonflexible grounded service raceway 

(4) Any grounded service enclosure 

(5) As provided by 250.32(B) 

Exception: The supplemental electrode shall be permitted 
to be bonded to the interior metal water piping at any 
convenient point as specified in 250.68(C)(1), Exception. 

(E) Supplemental Electrode Bonding Connection Size. 

Where the supplemental electrode is a rod, pipe, or plate 
electrode, that portion of the bonding jumper that is the sole 
connection to the supplemental grounding electrode shall 
not be required to be larger than 6 AWG copper wire or 4 
AWG aluminum wire. 

(F) Ground Ring. The ground ring shall be buried at a depth 
below the earth's surface of not less than 750 mm (30 in.). 

(G) Rod and Pipe Electrodes. The electrode shall be in- 
stalled such that at least 2.44 m (8 ft) of length is in contact 
with the soil. It shall be driven to a depth of not less than 
2.44 m (8 ft) except that, where rock bottom is encoun- 
tered, the electrode shall be driven at an oblique angle not 
to exceed 45 degrees from the vertical or, where rock bottom 
is encountered at an angle up to 45 degrees, the electrode shall 
be permitted to be buried in a trench that is at least 750 mm 
(30 in.) deep. The upper end of the electrode shall be flush 
with or below ground level unless the aboveground end and 
the grounding electrode conductor attachment are protected 
against physical damage as specified in 250.10. 

(H) Plate Electrode. Plate electrodes shall be installed not 
less than 750 mm (30 in.) below the surface of the earth. 

250.54 Auxiliary Grounding Electrodes. One or more 
grounding electrodes shall be permitted to be connected to 
the equipment grounding conductors specified in 250.118 



and shall not be required to comply with the electrode 
bonding requirements of 250.50 or 250.53(C) or the resis- 
tance requirements of 250.53(A)(2) Exception, but the 
earth shall not be used as an effective ground-fault current 
path as specified in 250.4(A)(5) and 250.4(B)(4). 

250.58 Common Grounding Electrode. Where an ac sys- 
tem is connected to a grounding electrode in or at a build- 
ing or structure, the same electrode shall be used to ground 
conductor enclosures and equipment in or on that building or 
structure. Where separate services, feeders, or branch circuits 
supply a building and are required to be connected to a 
grounding electrode(s), the same grounding electrode(s) shall 
be used. 

Two or more grounding electrodes that are bonded to- 
gether shall be considered as a single grounding electrode 
system in this sense. 

250.60 Use of Strike Termination Devices. Conductors 
and driven pipes, rods, or plate electrodes used for ground- 
ing strike termination devices shall not be used in lieu of 
the grounding electrodes required by 250.50 for grounding 
wiring systems and equipment. This provision shall not 
prohibit the required bonding together of grounding elec- 
trodes of different systems. 

Informational Note No. 1: See 250.106 for spacing from 
strike termination devices. See 800.100(D), 8 10.21 (J), and 
820.100(D) for bonding of electrodes. 

Informational Note No. 2: Bonding together of all sepa- 
rate grounding electrodes will limit potential differences 
between them and between their associated wiring systems. 

250.62 Grounding Electrode Conductor Material. The 

grounding electrode conductor shall be of copper, alumi- 
num, or copper-clad aluminum. The material selected shall 
be resistant to any corrosive condition existing at the instal- 
lation or shall be protected against corrosion. The conduc- 
tor shall be solid or stranded, insulated, covered, or bare. 

250.64 Grounding Electrode Conductor Installation. 

Grounding electrode conductors at the service, at each 
building or structure where supplied by a feeder(s) or 
branch circuit(s), or at a separately derived system shall be 
installed as specified in 250.64(A) through (F). 

(A) Aluminum or Copper-Clad Aluminum Conductors. 

Bare aluminum or copper-clad aluminum grounding elec- 
trode conductors shall not be used where in direct contact 
with masonry or the earth or where subject to corrosive 
conditions. Where used outside, aluminum or copper-clad 
aluminum grounding electrode conductors shall not be ter- 
minated within 450 mm (18 in.) of the earth. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-113 



250.64 



ARTICLE 250 — GROUNDING AND BONDING 



(B) Securing and Protection Against Physical Damage. 

Where exposed, a grounding electrode conductor or its en- 
closure shall be securely fastened to the surface on which it 
is carried. Grounding electrode conductors shall be permit- 
ted to be installed on or through framing members. A 4 
AWG or larger copper or aluminum grounding electrode 
conductor shall be protected if exposed to physical damage. 
A 6 AWG grounding electrode conductor that is free from 
exposure to physical damage shall be permitted to be run 
along the surface of the building construction without metal 
covering or protection if it is securely fastened to the con- 
struction; otherwise, it shall be protected in rigid metal 
conduit (RMC), intermediate metal conduit (IMC), rigid 
polyvinyl chloride conduit (PVC). reinforced thermosetting 
resin conduit (RTRC). electrical metallic tubing (EMT). or 
cable armor. Grounding electrode conductors smaller than 6 
AWG shall be protected in RMC. IMC. PVC. RTRC. EMT, 
or cable armor. 

(C) Continuous. Except as provided in 250.30(A)(5) and 
(A)(6). 250.30(B)(1), and 250.68(C). grounding electrode 
conductor(s) shall be installed in one continuous length 
without a splice or joint. If necessary, splices or connec- 
tions shall be made as permitted in (1) through (4): 

(1) Splicing of the wire-type grounding electrode conduc- 
tor shall be permitted only by irreversible compression- 
type connectors listed as grounding and bonding equip- 
ment or by the exothermic welding process. 

(2) Sections of busbars shall be permitted to be connected 
together to form a grounding electrode conductor. 

(3) Bolted, riveted, or welded connections of structural 
metal frames of buildings or structures. 

(4) Threaded, welded, brazed, soldered or bolted-flange 
connections of metal water piping. 

(D) Service with Multiple Disconnecting Means Enclo- 
sures. If a service consists of more than a single enclosure 
as permitted in 230.71(A), grounding electrode connections 
shall be made in accordance with 250.64(D)(1), (D)(2), or 
(D)(3). 

(1) Common Grounding Electrode Conductor and Taps. 

A common grounding electrode conductor and grounding 
electrode conductor taps shall be installed. The common 
grounding electrode conductor shall be sized in accordance 
with 250.66, based on the sum of the circular mil area of 
the largest ungrounded service-entrance conductor(s). If the 
service -entrance conductors connect directly to a service 
drop or service lateral, the common grounding electrode 
conductor shall be sized in accordance with Table 250.66, 
Note 1. 

A grounding electrode conductor tap shall extend to the 
inside of each service disconnecting means enclosure. The 
grounding electrode conductor taps shall be sized in accor- 



dance with 250.66 for the largest service-entrance conduc- 
tor serving the individual enclosure. The tap conductors 
shall be connected to the common grounding electrode con- 
ductor by one of the following methods in such a manner 
that the common grounding electrode conductor remains 
without a splice or joint: 

(1) Exothermic welding 

(2) Conno tor listed as grounding and bonding equipment. 

(3) Connections to an aluminum or copper busbar not less 
than 6 mm x 50 mm (>/t in. x 2 in.). The busbar shall be 
securely fastened and shall be installed in an accessible 
location. Count ./>;.>ns shall be made by a li ited connec- 
tor or bv the exothermic welding proi ess. If aluminum 
busbars are used, the installation shall comply with 
250.64(A). 

(2) Individual Grounding Electrode Conductors. A 

grounding electrode conductor shall be connected between 
the grounded conductor in each service equipment discon- 
necting means enclosure and the grounding electrode sys- 
tem. Each grounding electrode conductor shall be sized in 
accordance with 250.66 based on the service-entrance con- 
ductors) supplying the individual service disconnecting 
means. 

(3) Common Location. A grounding electrode conductor 
shall be connected to the grounded service conductor(s) in 
a wireway or other accessible enclosure on the supply side 
of the service disconnecting means. The connection shall 
be made with exothermic welding or a connector listed as 
grounding and bonding equipment. The grounding elec- 
trode conductor shall be sized in accordance with 250.66 
based on the service-entrance conductor(s) at the common 
location where the connection is made. 

(E) Enclosures for Grounding Electrode Conductors. 

Ferrous metal enclosures for grounding electrode conduc- 
tors shall be electrically continuous from the point of at- 
tachment to cabinets or equipment to the grounding elec- 
trode and shall be securely fastened to the ground clamp or 
fitting. Nonferrous metal enclosures shall not be required to 
be electrically continuous. Ferrous metal enclosures that are 
not physically continuous from cabinets or equipment to 
the grounding electrode shall be made electrically continuous 
by bonding each end of the raceway or enclosure to the 
grounding electrode conductor. Bonding methods in compli- 
ance with 250.92(B) for installations at sen-ice equipment lo- 
cations and with 250.92(B)(2) through (B)(4) for other than 
service equipment locations shall apply at each end and to all 
intervening ferrous raceways, boxes, and enclosures between 
the cabinets or equipment and the grounding electrode. The 
bonding jumper for a grounding electrode conductor raceway 
or cable armor shall be the same size as, or larger than, the 
enclosed grounding electrode conductor. If a raceway is used 
as protection for a grounding electrode conductor, the instal- 



70-114 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.68 



lation shall comply with the requirements of the appropriate 
raceway article. 

(F) Installation to Electrode(s). Grounding electrode con- 
ductors) and bonding jumpers interconnecting grounding 
electrodes shall be installed in accordance with (1), (2), or 
(3). The grounding electrode conductor shall be sized for 
the largest grounding electrode conductor required among 
all the electrodes connected to it. 

(1) The grounding electrode conductor shall be permitted 
to be run to any convenient grounding electrode avail- 
able in the grounding electrode system where the other 
electrode(s), if any, is connected by bonding jumpers 
that are installed in accordance with 250.53(C). 

(2) Grounding electrode conductor(s) shall be permitted to be 
run to one or more grounding electrode(s) individually. 

(3) Bonding jumper(s) from grounding electrode(s) shall 
be permitted to be connected to an aluminum or copper 
busbar not less than 6 mm x 50 mm QA in. x 2 in.). The 
busbar shall be securely fastened and shall be installed 
in an accessible location. Connections shall be made by 
a listed connector or by the exothermic welding process. 
The grounding electrode conductor shall be permitted to 
be run to the busbar. Where aluminum busbars are used, 
the installation shall comply with 250.64(A). 

250.66 Size of Alternating-Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor at the service, at each building or structure where 
supplied by a feeder(s) or branch circuit(s), or at a sepa- 
rately derived system of a grounded or ungrounded ac sys- 
tem shall not be less than given in Table 250.66, except as 
permitted in 250.66(A) through (C). 

Informational Note: See 250.24(C) for size of ac system 
conductor brought to service equipment. 

(A) Connections to Rod, Pipe, or Plate Electrodes. 

Where the grounding electrode conductor is connected to 
rod, pipe, or plate electrodes as permitted in 250.52(A)(5) 
or (A)(7), that portion of the conductor that is the sole connec- 
tion to the grounding electrode shall not be required to be 
larger than 6 AWG copper wire or 4 AWG aluminum wire. 

(B) Connections to Concrete-Encased Electrodes. 

Where the grounding electrode conductor is connected to a 
concrete-encased electrode as permitted in 250.52(A)(3), 
that portion of the conductor that is the sole connection to 
the grounding electrode shall not be required to be larger 
than 4 AWG copper wire. 

(C) Connections to Ground Rings. Where the grounding 
electrode conductor is connected to a ground ring as permitted 
in 250.52(A)(4), that portion of the conductor that is the sole 
connection to the grounding electrode shall not be required to 
be larger than the conductor used for the ground ring. 



Table 250.66 Grounding Electrode Conductor for 
Alternating-Current Systems 



Size of Largest Ungrounded 

Service-Entrance 

Conductor or Equivalent 

Area for Parallel 
Conductors 3 (AWG/kcmil) 



Size of Grounding Electrode 
Conductor (AWG/kcmil) 



Copper 



Aluminum or 

Copper-Clad 

Aluminum 



Copper 



Aluminum or 
Copper- Clad 
Aluminum 1 " 



2 or smaller 


1/0 or smaller 


8 


6 


1 or 1/0 


2/0 or 3/0 


6 


4 


2/0 or 3/0 


4/0 or 250 


4 


2 


Over 3/0 
through 
350 


Over 250 
through 500 


2 


1/0 


Over 350 
through 
600 


Over 500 
through 900 


1/0 


3/0 


Over 600 
through 
1100 


Over 900 
through 1750 


2/0 


4/0 


Over 1100 


Over 1750 


3/0 


250 



Notes: 

1. Where multiple sets of service-entrance conductors are used as 
permitted in 230.40, Exception No. 2, the equivalent size of the larg- 
est service-entrance conductor shall be determined by the largest sum 
of the areas of the corresponding conductors of each set. 

2. Where there are no service-entrance conductors, the grounding 
electrode conductor size shall be determined by the equivalent size of 
the largest service-entrance conductor required for the load to be 
served. 

"This table also applies to the derived conductors of separately de- 
rived ac systems. 
b See installation restrictions in 250.64(A). 



250.68 Grounding Electrode Conductor and Bonding 
Jumper Connection to Grounding Electrodes. The con- 
nection of a grounding electrode conductor at the service, at 
each building or structure where supplied by a feeder(s) or 
branch circuit(s), or at a separately derived system and as- 
sociated bonding jumper(s) shall be made as specified 
250.68(A) through (C). 

(A) Accessibility. All mechanical elements used to termi- 
nate a grounding electrode conductor or bonding jumper to 
a grounding electrode shall be accessible. 

Exception No. 1: An encased or buried connection to a 
concrete-encased, driven, or buried grounding electrode 
shall not be required to be accessible. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-115 



250.70 



ARTICLE 250 — GROUNDING AND BONDING 



Exception No. 2: Exothermic or irreversible compression 
connections used at terminations, together with the me- 
chanical means used to attach such terminations to fire- 
proofed structural metal whether or not the mechanical 
means is reversible, shall not be required to be accessible. 

(B) Effective Grounding Path. The connection of a 
grounding electrode conductor or bonding jumper to a 
grounding electrode shall be made in a manner that will 
ensure an effective grounding path. Where necessary to ensure 
the grounding path for a metal piping system used as a 
grounding electrode, bonding shall be provided around insu- 
lated joints and around any equipment likely to be discon- 
nected for repairs or replacement. Bonding jumpers shall be of 
sufficient length to permit removal of such equipment while 
retaining the integrity of the grounding path. 

(C) Metallic Water IMpc and Structural Vltlal. Groi rid 

ing electrode conductors and bonding jumpers shaH be pea 

mitted to b< connected n ili> follov m 1 : lo.., '.on and u ;d 

to extend the connection to an electrode(s): 

(1) Interior uiual water piping located no! more than L52 m 
(5 ft) from the point ol entrance to '.he building shall he 
i cuiiihi-H to \ r used a-- a conductor to im rconn^ct elec- 
trodes tin ai • pari of the g bunding <*V c rod* system. 

Exception: In industrial, commercial and institutional 
buildings or structures, if conditions of maintenance and 
sup rwvi ti'Si: . tha only '.qualified persons seiyict the 
>' •tallniiov. ir.h koi a ;•;! watei ij ; p;t y located more than 
1.52 in (5 if) from the faint of < nt ranee to the building shall 
be permitted as a bonding conductor to intercoiinecl elec- 
trodt ;. that are part i [the grounding electrode system, or as 
a grounding electrodi conductot if the . m re length, othei 
than short sections passing perpendicularly through walls, 
floors, oi !t/<'u<" 1 o] the interiot metal watei <«/'« '/''"■ is 
being used foi tht conductoi is exposed. 

IT) The tAi'icntrtl iiani^ of a building .ti.tt is dii ctly ct i- 
nected to a grounding electrode as specified in 
250.52(A)(2): or 250.68(C)(2)(a), (b), or (c) Shall be 
permitti J as a. bonding < onductor to mtu', 1 * •imect elec- 
trodes that are part of h\ gicnuling elcurodt system, 
or as 'i grounding electrode coiiducloi 

a. By connecting )fae structural metal frame to the re- 
inforcing bars of a concrete-encased electrode, as 
provided in 250.52(A)(3), os ground ring as pro- 
vided in 250.52(A)(4) 

b. By bonding the structural metal frame to one or 
more of the g'oim'iinj electrodes as specified in 
250.52(A)(5) or (A)(7), that comply with (2) 

c. i j v)ili j r .j.pi '»• M means of :stabli hing a eonnec 
tion to earth 



250.70 Methods of Grounding and Bonding Conductor 
Connection to Electrodes. The grounding or bonding con- 
ductor shall be connected to the grounding electrode by 
exothermic welding, listed lugs, listed pressure connectors, 
listed clamps, or other listed means. Connections depend- 
ing on solder shall not be used. Ground clamps shall be 
listed for the materials of the grounding electrode and the 
grounding electrode conductor and, where used on pipe, 
rod, or other buried electrodes, shall also be listed for direct 
soil burial or concrete encasement. Not more than one con- 
ductor shall be connected to the grounding electrode by a 
single clamp or fitting unless the clamp or fitting is listed 
for multiple conductors. One of the following methods 
shall be used: 

(1) A pipe fitting, pipe plug, or other approved device 
screwed into a pipe or pipe fitting 

(2) A listed bolted clamp of cast bronze or brass, or plain 
or malleable iron 

(3) For indoor communications purposes only, a listed 
sheet metal strap-type ground clamp having a rigid 
metal base that seats on the electrode and having a 
strap of such material and dimensions that it is not 
likely to stretch during or after installation 

(4) An equally substantial approved means 

IV. Enclosure, Raceway, and Service Cable 
Connections 

250.80 Service Raceways and Enclosures. Metal enclo- 
sures and raceways for service conductors and equipment 
shall be connected to the grounded system conductor if the 
electrical system is grounded or to the grounding electrode 
conductor for electrical systems that are not grounded. 

Exception: A metal elbow that is installed in an underground 
nam u tallk m, i » <ay and is isolated from possible contact by 
a minimum cover of 450 mm (18 in.) to any part of the elbow 
shall not be required to be connected to the grounded system 
conductor or grounding electrode conductor. 

250.84 Underground Service Cable or Raceway. 

(A) Underground Service Cable. The sheath or armor of 
a continuous underground metal-sheathed or armored ser- 
vice cable system that is connected to the grounded system 
conductor on the supply side shall not be required to be 
connected to the grounded system conductor at the building 
or structure. The sheath or armor shall be permitted to be 
insulated from the interior metal raceway or piping. 

(B) Underground Service Raceway Containing Cable. 

An underground metal service raceway that contains a 
metal-sheathed or armored cable connected to the grounded 
system conductor shall not be required to be connected to 
the grounded system conductor at the building or structure. 
The sheath or armor shall be permitted to be insulated from 
the interior metal raceway or piping. 



70-116 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.94 



250.86 Other Conductor Enclosures and Raceways. Ex- 
cept as permitted by 250.112(1), metal enclosures and race- 
ways for other than service conductors shall be connected 
to the equipment grounding conductor. 

Exception No. 1: Metal enclosures and raceways for con- 
ductors added to existing installations of open wire, knob- 
and-tube wiring, and nonmetallic-sheathed cable shall not 
be required to be connected to the equipment grounding 
conductor where these enclosures or wiring methods com- 
ply with (1) through (4) as follows: 

(1) Do not provide an equipment ground 

(2) Are in runs of less than 7.5 m (25 ft) 

(3) Are free from probable contact with ground, grounded 
metal, metal lath, or other conductive material 

(4) Are guarded against contact by persons 

Exception No. 2: Short sections of metal enclosures or 
raceways used to provide support or protection of cable 
assemblies from physical damage shall not be required to 
be connected to the equipment grounding conductor. 

Exception No. 3: A metal elbow shall not be required to be 
connected to the equipment grounding conductor where it 
is installed in a run of nonmetallic raceway and is isolated 
from possible contact by a minimum cover of 450 mm 
(18 in.) to any part of the elbow or is encased in not less 
than 50 mm (2 in.) of concrete. 

V. Bonding 

250.90 General. Bonding shall be provided where neces- 
sary to ensure electrical continuity and the capacity to con- 
duct safely any fault current likely to be imposed. 

250.92 Services. 

(A) Bonding of Equipment for Services. The normally 
non-current-carrying metal parts of equipment indicated in 
250.92(A)(1) and (A)(2) shall be bonded together. 

(1) All raceways, cable trays, cablebus framework, auxil- 
iary gutters, or service cable armor or sheath that en- 
close, contain, or support service conductors, except as 
permitted in 250.80 

(2) All enclosures containing service conductors, including 
meter fittings, boxes, or the like, interposed in the ser- 
vice raceway or armor 

(B) Method of Bonding at the Service. Bonding jumpers 
meeting the requirements of this article shall be used 
around impaired connections, such as reducing washers or 
oversized, concentric, or eccentric knockouts. Standard 
lockouts or bushings shall not be the only means for the bond- 
ing required by this section but shall be permitted to be in- 
stalled to make a mechanical connection <>» *K i u ew ay(s). 



Electrical continuity at service equipment, service race- 
ways, and service conductor enclosures shall be ensured by 
one of the following methods: 

(1) Bonding equipment to the grounded service conductor 
in a manner provided in 250.8 

(2) Connections utilizing threaded couplings or threaded 
hubs on enclosures if made up wrenchtight 

(3) Threadless couplings and connectors if made up tight 
for metal raceways and metal-clad cables 

(4) Other listed devices, such as bonding-type locknuts, bush- 
ings, or bushings with bonding jumpers 

250.94 Bonding for Other Systems. An intersystem bond- 
ing termination for connecting intersystem bonding con- 
ductors required for other systems shall be provided exter- 
nal to enclosures at the service equipment or metering 
equipment enclosure and at the disconnecting means for 
any additional buildings or structures. The intersystem 
bonding termination shall comply with the following: 

(1) Be accessible for connection and inspection. 

(2) Consist of a set of terminals with the capacity for con- 
nection of not less than three intersystem bonding con- 
ductors. 

(3) Not interfere with opening the enclosure for a service, 
building or structure disconnecting means, or metering 
equipment, 

(4) At the service equipment, be securely mounted and 
electrically connected to an enclosure for the service 
equipment, to the meter enclosure, or to an exposed 
nonilexible metallic service raceway, or be mounted at 
one of these enclosures and be connected to the enclo- 
sure or to the grounding electrode conductor with a 
minimum 6 AWG copper conductor 

(5) At the disconnecting means for a building or structure, 
be securely mounted and electrically connected to the 
metallic enclosure for the building or structure discon- 
necting means, or be mounted at the disconnecting 
means and be connected to the metallic enclosure or to 
the grounding electrode conductor with a minimum 6 
AWG copper conductor. 

(6) The terminals shall be listed as grounding and bonding 
equipment. 

Exception: In existing buildings or structures where any of 
the intersystem bonding and grounding electrode conductors 
required by 770.100(B)(2), 800.100(B)(2), 81 0.21(E)(2), 
820.100(B)(2), and 830.100(B)(2) exist, installation of the in- 
tersystem. bonding termination is not required. An accessible 
means external to enclosures for connecting intersystem bond- 
ing and grounding electrode conductors shall be permitted at 
the service equipment and at the disconnecting means for any 
additional buildings or structures by at least one of the follow- 
ing means: 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-117 



250.96 



ARTICLE 250 — GROUNDING AND BONDING 



(J) Exposed nonflexible metallic raceways 

(2) An exposed grounding electrode conductor 

(3) Approved means for the external connection of a cop- 
per or other corrosion-resistant bonding or grounding 
electrode conductor to the grounded raceway or 
equipment 

Informational Note No. 1: A 6 AWG copper conductor 
with one end bonded to the grounded nonflexible metallic 
raceway or equipment and with 1 50 mm (6 in.) or more of 
the other end made accessible on the outside wall is an 
example of the approved means covered in 250.94, Excep- 
tion item (3). 

Informational Note No. 2: See 770,100, 800.100, 810.21, 
820.100, and 830.100 for intersystem bonding and ground- 
ing requirements for conductive optical fiber cables, com- 
munications circuits, radio and television equipment, 
CATV circuits and network-powered broadband communi- 
cations systems respectively. 

250.96 Bonding Other Enclosures. 

(A) General. Metal raceways, cable trays, cable armor, 
cable sheath, enclosures, frames, fittings, and other metal 
non-current-carrying parts that are to serve as equipment 
grounding conductors, with or without the use of supple- 
mentary equipment grounding conductors, shall be bonded 
where necessary to ensure electrical continuity and the ca- 
pacity to conduct safely any fault current likely to be im- 
posed on them. Any nonconductive paint, enamel, or simi- 
lar coating shall be removed at threads, contact points, and 
contact surfaces or be connected by means of fittings de- 
signed so as to make such removal unnecessary. 

(B) Isolated Grounding Circuits. Where installed for the 
reduction of electrical noise (electromagnetic interference) 
on the grounding circuit, an equipment enclosure supplied 
by a branch circuit shall be permitted to be isolated from a 
raceway containing circuits supplying only that equipment 
by one or more listed nonmetallic raceway fittings located 
at the point of attachment of the raceway to the equipment 
enclosure. The metal raceway shall comply with provisions of 
this article and shall be supplemented by an internal insulated 
equipment grounding conductor installed in accordance with 
250.146(D) to ground the equipment enclosure. 

Informational Note: Use of an isolated equipment ground- 
ing conductor does not relieve the requirement for ground- 
ing the raceway system. 

250.97 Bonding for Over 250 Volts, For circuits of over 
250 volts to ground, the electrical continuity of metal race- 
ways and cables with metal sheaths that contain any con- 
ductor other than service conductors shall be ensured by 
one or more of the methods specified for services in 
250.92(B), except for (B)(1). 

Exception: Where oversized, concentric, or eccentric knock- 
outs are not encountered, or where a box or enclosure with 



concentric or eccentric knockouts is listed to provide a 
reliable bonding connection, the following methods shall be 
permitted: 

(1) Threadless couplings and connectors for cables with 
metal sheaths 

(2) Two locknuts, on rigid metal conduit or intermediate 
metal conduit, one inside and one outside of boxes and 
cabinets 

(3) Fittings with shoulders that seat firmly against the box 
or cabinet, such as electrical metallic tubing connec- 
tors, flexible metal conduit connectors, and cable con- 
nectors, with one locknut on the inside of boxes and 
cabinets 

(4) Listed fittings 

250.98 Bonding Loosely Jointed Metal Raceways. Ex 

pansion fittings and telescoping sections of metal raceways 
shall be made electrically continuous by equipment bond- 
ing jumpers or other means. 

250.100 Bonding in Hazardous (Classified) Locations. 

Regardless of the voltage of the electrical system, the elec- 
trical continuity of non-current-carrying metal parts of 
equipment, raceways, and other enclosures in any hazard- 
ous (classified) location as defined in 500.5 shall be ensured 
by any of the bonding methods specified in 250.92(B)(2) 
through (B)(4). One or more of these bonding methods 
shall be used whether or not equipment grounding conduc- 
tors of the wire type are installed. 

250.102 Bonding Conductors and Jumpers. 

(A) Material. Bonding jumpers shall be of copper or other 
corrosion-resistant material. A bonding jumper shall be a 
wire, bus, screw, or similar suitable conductor. 

(B) Attachment. Bonding jumpers shall be attached in the 
manner specified by the applicable provisions of 250.8 
for circuits and equipment and by 250.70 for grounding 
electrodes. 

(C) Size — Sup:* v Si lo bonding Jumper. 

(1) Size for Supply Conductors in a Single Raceway or 

Ci'ile. The suppl} ide bonding jumper shall not be 
smaller than the sizes shown in Table 250.66 for grounding 
electrode conductors. Where the ungrounded -,uf r«ly con- 
ductors are larger than 1100 kcmil copper or 1750 kcmil 
aluminum, the supply-side bonding jumper shall have an 
area not less than 12V4 percent of the area of the largest set 
of: ungrounded supply conductors. 

(2) Size for Par.jH<-. Conductor iHStalliitv.n-s, Where the 
ungrounded suppl) conductor; are (/.nallcied in two or 
more raceways oi cables, and an individual fiipply-side 



70- 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.104 



bonding jurapei i,< used for Kmdiu;" these raceways oi 
cables (he i/c M the supply-side bonding tumpi' i< r : th 

it, ,-. .v ty oi c ible shall I e sekuci !inn> 1 'b'C 250 66 based 
oil fh.* size of the ungrounded supply conductors n :nh 
raceway oi cable. A single supply-side bonding jumper in- 
stalled for bonding two or more raceways oi cables shall be 
sized in accordance with 250 102(C)(1). 

(3) DiPt'itj'* M« .eiliih 'Mieiu the ungrounded supply 
conductor .Hid !ii f supply-side bonding jumper are of c if- 
fVu ci materials -opp'i or aluminum) the nuuiinui!! size 
of the Mpi>'\ "de iv'M»iin.' jumper shah* v. lusc.<) on Sl-c 
assumed i> e of nn^roinvl"! • onductoi , of the L >.imr in ti :- 
rial as th<. si ,5pl ; side bonding lumper uil .wth 'in aiup-n 
ity equivalent to that ot the installed uii'.riju'lcd supply 
conductors. 

(D) Size — Equipment Bonding Jumper on Load Side 
of an Overcurrent Device. The equipment bonding jumper 
on the load side of an overcurrent device(s) shall be sized 
in accordance wish 230.122. 

A single common continuous equipment bonding jumper 
shall be permitted to connect two or more raceways or cables 
if the bonding jumper is sized in accordance with 2~ : ; !22 for 
the largest overcurrent device supplying circuits therein. 

(E) Installation. Bonding jumpers or conductors and equip 
ment bonding jumpers shall be permitted to be installed inside 
or outside of a raceway or an enclosure. 

(1) Inside a Raccvi i> r . - In- 1 >sun . . i installed inside 
a raceway equipment bonding jumpers and bonding jump- 
ers oi conductors shall comply with tfk requirements of 
250.119 and 250. 148. 

(2) Outside a Racewiy or an Jejiclovjie If installed on 
thi oiitsidi the length of thi bonding jumper or conductoi 
or equipment buj'Ui.s.' jumper ' tisi LI not exceed I 8 m (6 ft) 
and sh-ih be routed wish the raceway oi en< losure. 

Exception: An equipment bonding jumper o> supph side 
, c'i'<hi>" i.iti'pei longer than 1.8 m (6 ft) shall he permitted 
at outside pole locations for the purpose of bonding or 
grounding isolated sections of metal raceways or elbows 
installed in exposed risers of metal conduit or other metal 
raceway, and fa i bonding grounding electrodes a. id shall 
noi bt requi -'J to be routed i itl a race \m oi em h urc 

(3) Protection. FiondsnE jumpers oi conductors and equip- 
ment bonding jumper: hall I » nstalled in iccordance with 
250.64(A) and (B). 

250.104 Bonding of Piping Systems and Exposed Struc- 
tural Steel. 

(A) Metal Water Piping. The metal water piping system 
shall be bonded as required in (A)(1), (A)(2), or (A)(3) of 



this section. The bonding jumper(s) shall be installed in 
accordance with 250.64(A), (B), and (E). The points of 
attachment of the bonding jumper(s) shall be accessible. 

(1) General. Metal water piping system(s) installed in or 
attached to a building or structure shall be bonded to the 
service equipment enclosure, the grounded conductor at the 
service, the grounding electrode conductor where of suffi- 
cient size, or to the one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with Table 
250.66 except as permitted in 250.104(A)(2) and (A)(3). 

(2) Buildings of Multiple Occupancy. In buildings of 
multiple occupancy where the metal water piping system(s) 
installed in or attached to a building or structure for the 
individual occupancies is metallically isolated from all 
other occupancies by use of nonmetallic water piping, the 
metal water piping system(s) for each occupancy shall be 
permitted to be bonded to the equipment grounding termi- 
nal of the panelboard or switchboard enclosure (other than 
service equipment) supplying that occupancy. The bonding 
jumper shall be sized in accordance with Table 250.122, 
based on the rating of the overcurrent protective device for 
the circuit supplying the occupancy. 

(3) Multiple Buildings or Structures Supplied by a 
Feeder(s) or Branch Circuit(s). The metal water piping 
system(s) installed in or attached to a building or structure 
shall be bonded to the building or structure disconnecting 
means enclosure where located at the building or structure, 
to the equipment grounding conductor run with the supply 
conductors, or to the one or more grounding electrodes 
used. The bonding jumper(s) shall be sized in accordance 
with 250.66, based on the size of the feeder or branch 
circuit conductors that supply the building. The bonding 
jumper shall not be required to be larger than the largest 
ungrounded feeder or branch circuit conductor supplying 
the building. 

(B) Other Metal Piping. If installed in, or attached to, a 
building or structure, a metal piping system(s), including 
gas piping, that is likely to become energized shall be 
bonded to the service equipment enclosure; the grounded 
conductor at the service; the grounding electrode conduc- 
tor, if of sufficient size; or to one or more grounding elec- 
trodes used. The bonding conductor(s) or jumper(s) shall be 
sized in accordance with 250.122, using the rating of the 
circuit that is likely to energize the piping system(s). The 
equipment grounding conductor for the circuit that is likely 
to energize the piping shall be permitted to serve as the 
bonding means. The points of attachment of the bonding 
jumper(s) shall be accessible. 

Informational Note No. 1: Bonding all piping and metal 
air ducts within the premises will provide additional safety. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-119 



250.106 



ARTICLE 250 — GROUNDING AND BONDING 



Informational Note No. 2: Additional inforrnaiiori for gas 
piping systems can he found in Section 7.1,; of NFPA 54- 
2009, National Fuel Gas Code. 

(C) Structural Metal. Exposed structural metal that is in- 
terconnected to form a metal building frame and is not 
intentionally grounded or bonded and is likely to become 
energized shall be bonded to the service equipment enclo- 
sure; the grounded conductor at the service: the <1]voii:ici1- 
<ii_< means foi l)iiilJ''ii\s os structures mi; plied K a feedei 
or branch circuit; the grounding electrode conductor, if of 
sufficient size; or to one or more grounding electrodes used. 
The bonding jumper(s) shall be sized in accordance with 
Table 250.66 and installed in accordance with 250.64(A), 
(B), and (E). The points of attachment of the bonding jump- 
ers) shall be accessible unless installed in compli irice with 
250.68(A). Exception No. 2. 

(D) Separately Derived Systems. Metal water piping sys- 
tems and structural metal that is interconnected to form a 
building frame shall be bonded to separately derived sys- 
tems in accordance with (D)(1) through (D)(3). 

(1) Metal Water Piping System(s). The grounded conduc- 
tor of each separately derived system shall be bonded to the 
nearest available point of the metal water piping system(s) 
in the area served by each separately derived system. This 
connection shall be made at the same point on the sepa- 
rately derived system where the grounding electrode con- 
ductor is connected. Each bonding jumper shall be sized in 
accordance with Table 250.66 based on the largest un- 
grounded conductor of the separately derived system. 

Exception No. J: A separate bonding jumper to the metal 
water piping system shall not be required where the metal 
water piping system is used as the grounding electrode for 
the separately derived system and the water piping system 
is in the area served. 

Exception No. 2: A separate water piping bonding jumper 
shall not be required where the metal frame of a building or 
structure is used as the grounding electrode for a sepa- 
rately derived system and. is bonded to the metal water 
piping in the area served by the separately derived system. 

(2) Structural Metal. Where exposed structural metal that 
is interconnected to form the building frame exists in the 
area served by the separately derived system, it shall be 
bonded to the grounded conductor of each separately de- 
rived system. This connection shall be made at the same 
point on the separately derived system where the grounding 
electrode conductor is connected. Each bonding jumper shall 
be sized in accordance with Table 250.66 based on the largest 
ungrounded conductor of the separately derived system. 

Exception No. 1: A separate bonding jumper to the build- 
ing structural metal shall not be required where the metal 



frame of a building or structure is used as the grounding 
electrode for the separately derived system. 

Exception No. 2: A separate bonding jumper to the build- 
ing structural metal shall not be required where the water 
piping of a building or structure is used as the grounding 
electrode for a separately derived system and is bonded to 
the building structural metal in the area served by the sepa- 
rately derived system. 

(3) Common Grounding Electrode Conductor. Where a 
common grounding electrode conductor is installed for 
multiple separately derived systems as permitted by 
250.30(A)(6), and exposed structural metal that is intercon- 
nected to form the building frame or interior metal piping 
exists in the area served by the separately derived system, 
the metal piping and the structural metal member shall be 
bonded to the common grounding electrode conductor in 
the area served by the separatel) derived system. 

Exception: A separate bonding jumper from each derived, 
system to metal water piping and to structured metal mem- 
bers shall not be required where the metal water piping and 
the structural metal members in the area served by the 
separately derived system are bonded to the common 
grounding electrode conductor. 

250.106 Lightning Protection Systems. The lightning 
protection system ground terminals shall be bonded to the 
building or structure grounding electrode system. 

Informational Note No. 1: See 250.60 for use of strike 
termination devices For further information, see 
NFPA 780-2011, Standard for the Installation of Lightning 
Protection Systems, which contains detailed information on 
grounding, bonding, and sideflash distance from lightning 
protection systems. 

Informational Note No. 2: Metal raceways, enclosures, 
frames, and other non-current-carrying metal parts of elec- 
trical equipment installed on a building equipped with a 
lightning protection system may require bonding or spacing 
from the lightning protection conductors in accordance 
with NFPA 780-2011, Standard for the Installation of 
Lightning Protection Systems. 



VI. Equipment Grounding and Equipment Grounding 
Conductors 

250.110 Equipment Fastened in Place (Fixed) or Con- 
nected by Permanent Wiring Methods. Exposed, nor- 
mally non-current-carrying metal parts of fixed equipment 
supplied by or enclosing conductors or components that are 
likely to become energized shall be connected to an equipment 
grounding conductor under any of the following conditions: 
(1) Where within 2.5 m (8 ft) vertically or 1.5 m (5 ft) 

horizontally of ground or grounded metal objects and 

subject to contact by persons 



70-120 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.114 



(2) Where located in a wet or damp location and not isolated 

(3) Where in electrical contact with metal 

(4) Where in a hazardous (classified) location as covered 
by Articles 500 through 517 

(5) Where supplied by a wiring method that provides an 
equipment grounding conductor, except as permitted 
by 250.86 Exception No. 2 for short sections of metal 
enclosures 

(6) Where equipment operates with any terminal at over 
150 volts to ground 

Exception No. 1 : If t xemph d I v ;pt i it I p 'ri lission, the 
nietul frame of electrically heated appliances that have the 
frame permanently and effectively insulated from ground 
shall not he required to he grounded. 

Exception No. 2: Distribution apparatus, such as trans- 
former and capacitor cases, mounted on wooden poles at a 
height exceeding 2.5 m (8 ft) above ground or grade level 
shall not he required to he grounded, 

Exception No. 3: Listed equipment protected by a system 
of double insulation, or its equivalent, shall not be required 
to be connected to the equipment grounding conductor. 
Where such a system is employed, the equipment shall be 
distinctively marked. 

250.112 Sped * Equipment Fastened in Place (Fixed) 
or Connected by Permanent Wiring M*wh&ds. Except as 

permitted in 250.1 12{Fi and (1). exposed, lvviiMlly non- 
current-carrying metal parts of equipment described in 
250.112(A) through (K), and normally non-current- 
carrying metal parts of equipment and enclosures described 
in 250.112(L) and (M), shall be connected to an equipment 
grounding conductor, regardless of voltage. 

(A) Switchboard Frames and Structures. Switchboard 
frames and structures supporting switching equipment, ex- 
cept frames of 2-wire dc switchboards where effectively 
insulated from ground. 

(B) Pipe Organs. Generator and motor frames in an elec- 
trically operated pipe organ, unless effectively insulated 
from ground and the motor driving it. 

(C) Motor Frames. Motor frames, as provided by 430.242. 

(D) Enclosures for Motor Controllers. Enclosures for 
motor controllers unless attached to ungrounded portable 
equipment. 

(E) Elevators and Cranes. Electrical equipment for eleva- 
tors and cranes. 



(F) Garages, Theaters, and Motion Picture Studios. 

Electrical equipment in commercial garages, theaters, and 
motion picture studios, except pendant lampholders sup- 
plied by circuits not over 150 volts to ground. 

(G) Electric Signs. Electric signs, outline lighting, and as- 
sociated equipment as provided in 600.7. 

(H) Motion Picture Projection Equipment. Motion pic- 
ture projection equipment. 

(I) Remote- Control, Signaling, and Fire Alarm Circuits. 

Equipment supplied by Class 1 circuits shall be grounded 
unless operating at less than 50 volts. Equipment supplied 
by Class 1 power-limited circuits, by Class 2 and Class 3 
remote-control and signaling circuits, and by fire alarm cir- 
cuits shall be grounded where system grounding is required 
by Part II or Part VIII of this article. 

(J) Luminaires. Luminaires as provided in Part V of Ar- 
ticle 410. 

(K) Skid-Mounted Equipment. Permanently mounted elec- 
trical equipment and skids shall be connected to the equipment 
grounding conductor sized as required by 250.122. 

(L) Motor-Operated Water Pumps. Motor-operated wa- 
ter pumps, including the submersible type. 

(M) Metal Well Casings. Where a submersible pump is 
used in a metal well casing, the well casing shall be con- 
nected to the pump circuit equipment grounding conductor. 

250.114 Equipment Connected by Cord and Plug. Under 
any of the conditions described in 250.114(1) through (4), 
exposed, noiifplly non-current-carrying metal parts of 
cord-and-plug-connected equipment shall be connected to 
the equipment grounding conductor. 

Exception: Listed tools, listed appliances, and listed equip- 
ment covered in 250.114(2) through (4) shall not be required 
to be connected to an equipment grounding conductor where 
protected by a system of double insulation or its equivalent. 
Double insulated equipment shall be distinctively marked. 

(1) In hazardous (classified) locations (see Articles 500 
through 517) 

(2) Where operated at over 150 volts to ground 

Exception No. 1: Motors, where guarded, shall not be re- 
quired to be connected to an equipment grounding conductor. 

Exception No. 2: Metal frames of electrically heated ap- 
pliances, exempted by special permission, shall not be re- 
quired to be connected to an equipment grounding conduc- 
tor, in which case the frames shall be permanently and 
effectively insulated from ground. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-121 



250.116 



ARTICLE 250 — GROUNDING AND BONDING 



(3) In residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; ranges; kitchen waste disposers; information 
technology equipment; sump pumps and electrical 
aquarium equipment 

c. Hand-held motor-operated tools, stationary and 
fixed motor-operated tools, and light industrial 
motor-operated tools 

d. Motor-operated appliances of the following types: 
hedge clippers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

(4) In other than residential occupancies: 

a. Refrigerators, freezers, and air conditioners 

b. Clothes-washing, clothes-drying, dish-washing ma- 
chines; information technology equipment; sump 
pumps and electrical aquarium equipment 

c. Hand-held motor-operated tools, stationary and 
fixed motor-operated tools, and light industrial 
motor-operated tools 

d. Motor-operated appliances of the following types: 
hedge clippers, lawn mowers, snow blowers, and 
wet scrubbers 

e. Portable handlamps 

f. Cord-and-plug-connected appliances used in damp or 
wet locations or by persons standing on the ground or 
on metal floors or working inside of metal tanks or 
boilers 

g. Tools likely to be used in wet or conductive locations 

Exception: Tools and portable handlamps likely to be used 
in wet or conductive locations shall not be required to be 
connected to an equipment grounding conductor where 
supplied through an isolating transformer with an un- 
grounded secondary of not over 50 volts. 

250.116 Nonelectrical Equipment. The metal parts of the 
following nonelectrical equipment described in this section 
shall be connected to the equipment grounding conductor: 

(1) Frames and tracks of electrically operated cranes and 
hoists 

(2) Frames of nonelectrically driven elevator cars to which 
electrical conductors are attached 

(3) Hand-operated metal shifting ropes or cables of electric 
elevators 

Informational Note: Where extensive metal in or on build- 
ings may become energized and is subject to personal con- 
tact, adequate bonding and grounding will provide addi- 
tional safety. 

250.118 Types of Equipment Grounding Conductors. 

The equipment grounding conductor run with or enclosing 



the circuit conductors shall be one or more or a combina- 
tion of the following: 

(1) A copper, aluminum, or copper-clad aluminum con- 
ductor. This conductor shall be solid or stranded; in- 
sulated, covered, or bare; and in the form of a wire or 
a busbar of any shape. 

(2) Rigid metal conduit. 

(3) Intermediate metal conduit. 

(4) Electrical metallic tubing. 

(5) Listed flexible metal conduit meeting all the following 
conditions: 

a. The conduit is terminated in listed fittings. 

b. The circuit conductors contained in the conduit are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

c. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible metal 
conduit in the same grcund faull current path does 
not exceed 1 .8 m (6 ft). 

d. If used to connect equipment where flexibility is nec- 
essary to minimi le the transmi isiori ol \ ibration from 
equipment <>i to provide flexibility iorcquipmuii thai 
requires movement after installation, an equipment 
grounding conductor shall be installed. 

(6) Listed liquidtight flexible metal conduit meeting all 
the following conditions: 

a. The conduit is terminated in listed fittings. 

b. For metric designators 12 through 16 (trade sizes 
3 /s through Va), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated at 20 amperes or less. 

c. For metric designators 21 through 35 (trade sizes 
3 A through 1 l A), the circuit conductors contained in 
the conduit are protected by overcurrent devices 
rated not more than 60 amperes and there is no 
flexible metal conduit, flexible metallic tubing, or 
liquidtight flexible metal conduit in trade sizes 
metric designators 12 through 16 (trade sizes 3 /s 
through Vt) in the ground-fault current path. 

d. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground Iji'Ii current 
path does not exceed 1.8 m (6 ft). 

e. If used to connect equipment where flexibility is 
necessary to minimize the transmission of vibra- 
tion from equipment or to provide flexibility for 
equipment that requires movement after installa- 
tion, an equipment grounding conductor shall be 
installed. 

(7) Flexible metallic tubing where the tubing is terminated 
in listed fittings and meeting the following conditions: 



70-122 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.120 



a. The circuit conductors contained in the tubing are 
protected by overcurrent devices rated at 20 am- 
peres or less. 

b. The combined length of flexible metal conduit and 
flexible metallic tubing and liquidtight flexible 
metal conduit in the same ground-fault current 
path does not exceed 1.8 m (6 ft). 

(8) Armor of Type AC cable as provided in 320.108. 

(9) The copper sheath of mineral-insulated, metal-sheathed 
cable. 

(1.0) Type MC cable m.if provides an effectn •: ground-fault 
current path in accordance with one or more of the 
following: 

a. It contains an insulated or uninsJaieJ equipment 
grounding conductoi in compliance with *~U 1 18i 1) 

b. The combined metallic sheath and uninsulated 
equipmenl grounding/bonding conductor of inter- 
locked metal tape- type MC cable that is listed and 
idcniinV't i>- .in equipmenl grounding conductor 

c. The metallic sheath oi the combined mel llic 
sheath and equipment grounding i onduetors of the 
smooth oi corrugated tube-type MC cable that is 
listed and identified as an equipment grounding 
conductor 

(11) Cable trays as permitted in 392.10 and 392.60. 

(12) Cablebus framework as permitted in 370.3. 

(13) Other listed electrically continuous metal raceways 
and listed auxiliary gutters. 

(14) Surface metal raceways listed for grounding. 

Informational Note: For effective ground-fault current 
path, see 250.2 Definition. 

250.119 Identification of Equipment Grounding Con- 
ductors. Unless required elsewhere in this Code, equip- 
ment grounding conductors shall be permitted to be bare, 
covered, or insulated. Individually covered or insulated 
equipment grounding conductors shall have a continuous 
outer finish that is either green or green with one or more 
yellow stripes except as permitted in this section. Conduc- 
tors with insulation or individual covering that is green, 
green with one or more yellow stripes, or otherwise identi- 
fied as permitted by this section shall not be used for un- 
grounded or grounded circuit conductors. 

Exception: Power-limited Class 2 or Class 3 rabies, power- 
limited fire alarm cables, or communications tables contain- 
ing only circuits operating at less than 50 volts where con- 
nected to equipment not required to be grounded in 
accordance with 150, 112(1) shall be permitted to use a con- 
ductor with green insulation or green with one or more yellow 
stripes for other than equipment grounding purposes. 



(A) Conductors Larger Than 6 AWG. Equipment ground- 
ing conductors larger than 6 AWG shall comply with 
250.119(A)(1) and (A)(2). 

(1) An insulated or covered conductor larger than 6 AWG 
shall be permitted, at the time of installation, to be 
permanently identified as an equipment grounding con- 
ductor at each end and at every point where the con- 
ductor is accessible. 

Exception: Conductors larger than 6 AWG shall not be 
required to be marked in conduit bodies that contain no 
splices or unused hubs. 

(2) Identification shall encircle the conductor and shall be 
accomplished by one of the following: 

a. Stripping the insulation or covering from the entire 
exposed length 

b. Coloring the insulation or covering green at the ter- 
mination 

c. Marking the insulation or covering with green tape 
or green adhesive labels at the termination 

(B) Multiconductor Cable. Where the conditions of main- 
tenance and supervision ensure that only qualified persons ser- 
vice the installation, one or more insulated conductors in a 
multiconductor cable, at the time of installation, shall be per- 
mitted to be permanently identified as equipment grounding 
conductors at each end and at every point where the conduc- 
tors are accessible by one of the following means: 

(1) Stripping the insulation from the entire exposed length 

(2) Coloring the exposed insulation green 

(3) Marking the exposed insulation with green tape or 
green adhesive labels 

(C) Flexible Cord. An uninsulated equipment grounding 
conductor shall be permitted, but, if individually covered, 
the covering shall have a continuous outer finish that is 
either green or green with one or more yellow stripes. 

250.120 Equipment Grounding Conductor Installation. 

An equipment grounding conductor shall be installed in 
accordance with 250.120(A), (B), and (C). 

(A) Raceway, Cable Trays, Cable Armor, Cablebus, or 
Cable Sheaths. Where it consists of a raceway, cable tray, 
cable armor, cablebus framework, or cable sheath or where 
it is a wire within a raceway or cable, it shall be installed in 
accordance with the applicable provisions in this Code us- 
ing fittings for joints and terminations approved for use 
with the type raceway or cable used. All connections, 
joints, and fittings shall be made tight using suitable tools. 

Informational Note: See the UL guide information on 
FHIT systems for equipment grounding conductors in- 
stalled in a raceway that are part of an electrical circuit 
protective system or a fire-rated cable listed to maintain 
circuit integrity. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-123 



250.121 



ARTICLE 250 — GROUNDING AND BONDING 



(B) Aluminum and Copper-Clad Aluminum Conductors. 

Equipment grounding conductors of bare or insulated alu- 
minum or copper-clad aluminum shall be permitted. Bare 
conductors shall not come in direct contact with masonry or 
the earth or where subject to corrosive conditions. Alumi- 
num or copper-clad aluminum conductors shall not be ter- 
minated within 450 mm (18 in.) of the earth. 

(C) Equipment Grounding Conductors Smaller Than 6 

AWG. Where not routed with circuit conductors as permit- 
ted in 250.130(C) and 250.134(B) Exception No. 2, equip- 
ment grounding conductors smallei i.ii,irs o AWG shall be 
protected from physical damage by an identified raceway or 
cable armor unless installed within hollow spaces of the 
framing members of buildings or structures and where not 
subject to physical damage. 

250.121 Use of Equipment Grounding Conductors. An 

equipment grounding conductor shall not be used as a 
grounding electrode conductor. 

250.122 Size of Equipment Grounding Conductors. 

(A) General. Copper, aluminum, or copper-clad aluminum 
equipment grounding conductors of the wire type shall not 
be smaller than shown in Table 250.122, but in no case shall 
they be required to be larger than the circuit conductors sup- 
plying the equipment. Where a cable tray, a raceway, or a 
cable armor or sheath is used as the equipment grounding 
conductor, as provided in 250.118 and 250.134(A), it shall 
comply with 250.4(A)(5) or (B)(4). 

Equipment grounding conductors shall be permitted r<> 
be sectioned within a multiconductor cable, provided the 
combined circular mil area complies with Table 250.122. 

(B) Increased in Size. Where ungrounded conductors are 
increased in size, equipment grounding conductors, where 
installed, shall be increased in size proportionately accord- 
ing to the circular mil area of the ungrounded conductors. 

(C) Multiple Circuits. Where a single equipment ground- 
ing conductor is run with multiple circuits in the same 
raceway, cable, or cable tray, it shall be sized for the largest 
overcurrent device protecting conductors in the raceway, 
cable, or cable tray. Equipment grounding conductors in- 
stalled in cable trays shall meet the minimum requirements 
of 392.10(B)(1)(c). 

(D) Motor Circuits. Equipment grounding conductors for 
motor circuits shall be sized in accordance with (D)(1) or 
(D)(2). 

(1) General. The equipment grounding conductor size 
shall not be smaller than determined by 250.122(A) based 
on the rating of the branch-circuit short-circuit and ground- 
fault protective device. 



(2) Instantaneous-Trip Circuit Breaker and Motor 
Short-Circuit Protector. Where the overcurrent device is 
an instantaneous-trip circuit breaker or a motor short-circuit 
protector, the equipment grounding conductor shall be sized 
not smaller than that given by 250.122(A) using the maximum 
permitted rating of a dual element time-delay fuse selected for 
branch-circuit short-circuit and ground-fault protection in ac- 
cordance with 430.52(C)(1), Exception No. 1. 

(E) Flexible Cord and Fixture Wire. The equipment 
grounding conductor in a flexible cord with the largest cir- 
cuit conductor 10 AWG or smaller, and the equipment 
grounding conductor used with fixture wires of any size in 
accordance with 240.5, shall not be smaller than 18 AWG 
copper and shall not be smaller than the circuit conductors. 
The equipment grounding conductor in a flexible cord with 
a circuit conductor larger than 10 AWG shall be sized in 
accordance with Table 250.122. 

(F) Conductors in Parallel. Where conductors are installed 
in parallel in multiple raceways or cables as permitted in 
310.10(H), the equipment grounding conductors where used, 
shall be installed in parallel in each raceway or cable. Where 
conductors are installed in parallel n"i the same raceway, cable, 
or cable tray as permitted in 310.10(H), a single equipment 
grounding conductoi shall be permitted. Equipmen* grounding 
conductors installed in cable tray shall meet the minimum 
requirements of 392. 1 0(B )( 1 )(c ). 

Each equipment grounding conductor shall be sized in 
compliance with 250.122. 

(G) Feeder Taps. Equipment grounding conductors run 
with feeder taps shall not be smaller than shown in Table 
250. 122 based on the rating of the overcurrent device ahead 
of the feeder but shall not be required to be larger than the 
tap conductors. 

250.124 Equipment Grounding Conductor Continuity. 

(A) Separable Connections. Separable connections such 
as those provided in drawout equipment or attachment 
plugs and mating connectors and receptacles shall provide 
for first-make, last-break of the equipment grounding con- 
ductor. First-make, last-break shall not be required where 
interlocked equipment, plugs, receptacles, and connectors 
preclude energization without grounding continuity. 

(B) Switches. No automatic cutout or switch shall be 
placed in the equipment grounding conductor of a premises 
wiring system unless the opening of the cutout or switch 
disconnects all sources of energy. 

250.126 Identification of Wiring Device Terminals. The 

terminal for the connection of the equipment grounding 
conductor shall be identified by one of the following: 



70-124 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.134 



Table 250.122 Minimum Size Equipment Grounding 
Conductors for Grounding Raceway and Equipment 



Rating or Setting of 
Automatic Overcurrent 
Device in Circuit Ahead 
of Equipment, Conduit, 

etc., Not Exceeding 
(Amperes) 



Size (AWG or kcmil) 



Copper 



Aluminum or 
Copper-Clad 
Aluminum* 



15 

20 

60 

100 



14 

12 

10 

8 



12 

10 

8 

6 



200 


6 


4 


300 


4 


2 


400 


3 


1 


500 


2 


1/0 


600 


1 


2/0 


800 


1/0 


3/0 


1000 


2/0 


4/0 


1200 


3/0 


250 


1600 


4/0 


350 


2000 


250 


400 


2500 


350 


600 


3000 


400 


600 


4000 


500 


750 


5000 


700 


1200 


6000 


800 


1200 



Note: Where necessary to comply with 250.4(A)(5) or (B)(4), the 

equipment grounding conductor shall be sized larger than given in this 

table. 

*See installation restrictions in 250.120. 



(1) A green, not readily removable terminal screw with a 
hexagonal head. 

(2) A green, hexagonal, not readily removable terminal nut. 

(3) A green pressure wire connector. If the terminal for the 
grounding conductor is not visible, the conductor entrance 
hole shall be marked with the word green or ground, the 
letters G or GR, a grounding symbol, or otherwise identi- 
fied by a distinctive green color. If the terminal for the 
equipment grounding conductor is readily removable, the 
area adjacent to the terminal shall be similarly marked. 

Informational Note: See Informational Note Figure 250.126. 



Informational Note Figure 250.126 One Example of a Symbol 
Used to Identify the Grounding Termination Point for an 
Equipment Grounding Conductor. 



VII. Methods of Equipment Grounding 

250.130 Equipment Grounding Conductor Connections. 

Equipment grounding conductor connections at the source 
of separately derived systems shall be made in accordance 
with 250.30(A)(1). Equipment grounding conductor con- 
nections at service equipment shall be made as indicated in 
250.130(A) or (B). For replacement of non-grounding-type 
receptacles with grounding-type receptacles and for branch- 
circuit extensions only in existing installations that do not 
have an equipment grounding conductor in the branch circuit, 
connections shall be permitted as indicated in 250.130(C). 

(A) For Grounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to 
the grounded service conductor and the grounding elec- 
trode conductor. 

(B) For Ungrounded Systems. The connection shall be 
made by bonding the equipment grounding conductor to the 
grounding electrode conductor. 

(C) Nongrounding Receptacle Replacement or Branch 
Circuit Extensions. The equipment grounding conductor 
of a grounding-type receptacle or a branch-circuit extension 
shall be permitted to be connected to any of the following: 

(1) Any accessible point on the grounding electrode sys- 
tem as described in 250.50 

(2) Any accessible point on the grounding electrode con- 
ductor 

(3) The equipment grounding terminal bar within the en- 
closure where the branch circuit for the receptacle or 
branch circuit originates 

(4) For grounded systems, the grounded service conductor 
within the service equipment enclosure 

(5) For ungrounded systems, the grounding terminal bar 
within the service equipment enclosure 

Informational Note: See 406.4(D) for the use of a ground- 
fault circuit-interrupting type of receptacle. 

250.132 Short Sections of Raceway. Isolated sections of 
metal raceway or cable armor, where required to be grounded, 
shall be connected to an equipment grounding conductor in 
accordance with 250.134. 

250.134 Equipment Fastened in Place or Connected by 
Permanent Wiring Methods (Fixed) — Grounding. Un- 
less grounded by connection to the grounded circuit con- 
ductor as permitted by 250.32, 250.140, and 250.142, non- 
current-carrying metal parts of equipment, raceways, and 
other enclosures, if grounded, shall be connected to an 
equipment grounding conductor by one of the methods 
specified in 250.134(A) or (B). 



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70-125 



250.136 



ARTICLE 250 — GROUNDING AND BONDING 



(A) Equipment Grounding Conductor Types. By con- 
necting to any of the equipment grounding conductors per- 
mitted by 250.118. 

(B) With Circuit Conductors. By connecting to an equip- 
ment grounding conductor contained within the same race- 
way, cable, or otherwise run with the circuit conductors. 

Exception No. 1: As provided in 250.130(C), the equip- 
ment grounding conductor shall be permitted to be run 
separately from the circuit conductors. 

Exception No. 2: For dc circuits, the equipment grounding 
conductor shall be permitted to be run separately from the 
circuit conductors. 

Informational Note No. 1: See 250.102 and 250.168 for 
equipment bonding jumper requirements. 

Informational Note No. 2: See 400.7 for use of cords for 
fixed equipment. 

250.136 Equipment Considered Grounded. Under the 
conditions specified in 250.136(A) and (B), the normally 
non-current-carrying metal parts of the equipment shall be 
considered grounded. 

(A) Equipment Secured to Grounded Metal Supports. 

Electrical equipment secured to and in electrical contact 
with a metal rack or structure provided for its support and 
connected to an equipment grounding conductor by one of 
the means indicated in 250.134. The structural metal frame 
of a building shall not be used as the required equipment 
grounding conductor for ac equipment. 

(B) Metal Car Frames. Metal car frames supported by 
metal hoisting cables attached to or running over metal 
sheaves or drums of elevator machines that are connected 
to an equipment grounding conductor by one of the meth- 
ods indicated in 250.134. 

250.138 Cord-and-Plug-Connected Equipment. Non- 
current-carrying metal parts of cord-and-plug-connected 
equipment, if grounded, shall be connected to an equipment 
grounding conductor by one of the methods in 250.138(A) 
or (B). 

(A) By Means of an Equipment Grounding Conductor. 

By means of an equipment grounding conductor run with 
the power supply conductors in a cable assembly or flexible 
cord properly terminated in a grounding-type attachment 
plug with one fixed grounding contact. 

Exception: The grounding contacting pole of grounding- 
type plug-in ground-fault circuit interrupters shall be per- 
mitted to be of the movable, self- restoring type on circuits 
operating at not over 150 volts between any two conductors 
or over 150 volts between any conductor and ground. 



(B) By Means of a Separate Flexible Wire or Strap. By 

means of a separate flexible wire or strap, insulated or bare, 
connected to an equipment grounding conductor, and pro- 
tected as well as practicable against physical damage, 
where part of equipment. 

250.140 Frames of Ranges and Clothes Dryers. Frames 
of electric ranges, wall-mounted ovens, counter-mounted 
cooking units, clothes dryers, and outlet or junction boxes 
that are part of the circuit for these appliances shall be 
connected to the equipment grounding conductor in the 
manner specified by 250.134 or 250.138. 

Exception: For existing branch-circuit installations only 
where an equipment grounding conductor is not present in 
the outlet or junction box, the frames of electric ranges, 
wall-mounted ovens, counter-mounted cooking units, 
clothes dryers, and outlet or junction boxes that are part of 
the circuit for these appliances shall be permitted to be 
connected to the grounded circuit conductor if all the fol- 
lowing conditions are met. 

(1) The supply circuit is 120/240-volt, single-phase, 3 -wire; 
or 208Y/I20-volt derived from a 3 -phase, 4-wire, wye- 
connected system. 

(2) The grounded conductor is not smaller than 10 AWG 
copper or 8 AWG aluminum. 

(3) The grounded conductor is insulated, or the grounded 
conductor is uninsulated and part of a Type SE service- 
entrance cable and the branch circuit originates at the 
service equipment. 

(4) Grounding contacts of receptacles furnished as part of 
the equipment are bonded to the equipment. 

250.142 Use of Grounded Circuit Conductor for 
Grounding Equipment. 

(A) Supply-Side Equipment. A grounded circuit conduc- 
tor shall be permitted to ground non-current-carrying metal 
parts of equipment, raceways, and other enclosures at any 
of the following locations: 

(1) On the supply side or within the enclosure of the ac 
service-disconnecting means 

(2) On the supply side or within the enclosure of the main 
disconnecting means for separate buildings as provided 
in 250.32(B) 

(3) On the supply side or within the enclosure of the main 
disconnecting means or overcurrent devices of a sepa- 
rately derived system where permitted by 250.30(A)(1) 

(B) Load-Side Equipment. Except as permitted in 
250.30(A)(1) and 250.32(B) Exception, a grounded cir- 
cuit conductor shall not be used for grounding non- 
current-carrying metal parts of equipment on the load 
side of the service disconnecting means or on the load 



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NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.148 



side of a separately derived system disconnecting means 
or the overcurrent devices for a separately derived sys- 
tem not having a main disconnecting means. 

Exception No. 1: The frames of ranges, wall-mounted ov- 
ens, counter-mounted cooking units, and clothes dryers un- 
der the conditions permitted for existing installations by 
250.140 shall be permitted to be connected to the grounded 
circuit conductor. 

Exception No. 2: It shall be permissible to ground meter 
enclosures by connection to the grounded circuit conductor 
on the load side of the service disconnect where all of the 
following conditions apply: 

(1) No service ground-fault protection is installed. 

(2) All meter enclosures are located immediately adjacent 
to the service disconnecting means. 

(3) The size of the grounded circuit conductor is not 
smaller than the size specified in Table 250.122 for 
equipment grounding conductors. 

Exception No. 3: Direct-current systems shall be permitted 
to be grounded on the load side of the disconnecting means 
or overcurrent device in accordance with 250.164. 

Exception No. 4: Electrode-type boilers operating at over 
600 volts shall be grounded as required in 490.72(E)(1) 
and 490.74. 

250.144 Multiple Circuit Connections. Where equipment 
is grounded and is supplied by separate connection to more 
than one circuit or grounded premises wiring system, an 
equipment grounding conductor termination shall be provided 
for each such connection as specified in 250.134 and 250.138. 

250.146 Connecting Receptacle Grounding Terminal to 

Box. An equipment bonding jumper shall be used to con- 
nect the grounding terminal of a grounding-type receptacle 
to a grounded box unless grounded as in 250.146(A) 
through (D). The equipment bonding jumper shall be sized 
in accordance with Table 250. 122 based on the rating of the 
overcurrent device protecting the circuit conductors. 

(A) Surface-Mounted Box. Where the box is mounted on 
the surface, direct metal-to-metal contact between the de- 
vice yoke and the box or a contact yoke or device that 
complies with 250.146(B) shall be permitted to ground the 
receptacle to the box. At least one of the insulating washers 
shall be removed from receptacles that do not have a con- 
tact yoke or device that complies with 250.146(B) to ensure 
direct metal-to- metal contact. This provision shall not apply 
to cover-mounted receptacles unless the box and cover 
combination are listed as providing satisfactory ground 
continuity between the box and the receptacle. A listed ex- 
posed work cover shall be permitted to be the grounding 
and bonding means when (1) the device is attached to the 



cover with at least two fasteners that are permanent (such 
as a rivet) or have a thread locking or screw or nut locking 
means and (2) when the cover mounting holes are located 
on a flat non-raised portion of the cover. 

(B) Contact Devices or Yokes. Contact devices or yokes de- 
signed and listed as self-grounding shall be permitted in con- 
junction with the supporting screws to establish the grounding 
circuit between the device yoke and flush-type boxes. 

(C) Floor Boxes. Floor boxes designed for and listed as 
providing satisfactory ground continuity between the box 
and the device shall be permitted. 

(D) Isolated Receptacles. Where installed for the reduc- 
tion of electrical noise (electromagnetic interference) on the 
grounding circuit, a receptacle in which the grounding ter- 
minal is purposely insulated from the receptacle mounting 
means shall be permitted. The receptacle grounding termi- 
nal shall be connected to an insulated equipment grounding 
conductor run with the circuit conductors. This equipment 
grounding conductor shall be permitted to pass through one 
or more panelboards without a connection to the panel- 
board grounding terminal bar as permitted in 408.40, Ex- 
ception, so as to terminate within the same building or 
structure directly at an equipment grounding conductor ter- 
minal of the applicable derived system or service. Where 
installed in accordance with the provisions of this section, 
this equipment grounding conductor shall also be permitted 
to pass through boxes, wireways, or other enclosures with- 
out being connected to such enclosures. 

Informational Note: Use of an isolated equipment ground- 
ing conductor does not relieve the requirement for ground- 
ing the raceway system and outlet box. 

250.148 Continuity and Attachment of Equipment 
Grounding Conductors to Boxes. Where circuit conduc- 
tors are spliced within a box, or terminated on equipment 
within or supported by a box, any equipment grounding con- 
ductors) associated with those circuit conductors shall be con- 
nected within the box or to the box with devices suitable for 
the use in accordance with 250.148(A) through (E). 

Exception: The equipment grounding conductor permitted 
in 250.146(D) shall not be required to be connected to the 
other equipment grounding conductors or to the box. 

(A) Connections. Connections and splices shall be made 
in accordance with 110.14(B) except that insulation shall 
not be required. 

(B) Grounding Continuity. The arrangement of ground- 
ing connections shall be such that the disconnection or the 
removal of a receptacle, luminaire, or other device fed from 
the box does not interfere with or interrupt the grounding 
continuity. 



2011 Edition 



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70-127 



250.160 



ARTICLE 250 — GROUNDING AND BONDING 



(C) Metal Boxes. A connection shall be made between the 
one or more equipment grounding conductors and a metal 
box by means of a grounding screw that shall be used for 
no other purpose, equipment listed for grounding, or a 
listed grounding device. 

(D) Nonmetallic Boxes. One or more equipment ground- 
ing conductors brought into a nonmetallic outlet box shall 
be arranged such that a connection can be made to any 
fitting or device in that box requiring grounding. 

(E) Solder. Connections depending solely on solder shall 
not be used. 



VIII. Direct-Current Systems 

250.160 General. Direct-current systems shall comply 
with Part VIII and other sections of Article 250 not specifi- 
cally intended for ac systems. 

250.162 Direct-Current Circuits and Systems to Be 
Grounded. Direct-current circuits and systems shall be 
grounded as provided for in 250.162(A) and (B). 

(A) Two- Wire, Direct-Current Systems. A 2-wire, dc sys- 
tem supplying premises wiring and operating at greater than 
50 volts but not greater than 300 volts shall be grounded. 

Exception No. 1: A system equipped with a ground detec- 
tor and supplying only industrial equipment in limited ar- 
eas shall not be required to be grounded. 

Exception No. 2: A rectifier-derived dc system supplied 
from an ac system complying with 250.20 shall not be re- 
quired to be grounded. 

Exception No. 3: Direct-current fire alarm circuits having 
a maximum current of 0.030 ampere as specified in Article 
760, Part III, shall not be required to be grounded. 

(B) Three-Wire, Direct-Current Systems. The neutral 
conductor of all 3-wire, dc systems supplying premises wir- 
ing shall be grounded. 

250.164 Point of Connection for Direct-Current Systems. 

(A) Off-Premises Source. Direct-current systems to be 
grounded and supplied from an off-premises source shall 
have the grounding connection made at one or more supply 
stations. A grounding connection shall not be made at indi- 
vidual services or at any point on the premises wiring. 

(B) On-Premises Source. Where the dc system source is 
located on the premises, a grounding connection shall be 
made at one of the following: 

(1) The source 

(2) The first system disconnection means or overcurrent 
device 



(3) By other means that accomplish equivalent system pro- 
tection and that utilize equipment listed and identified 
for the use 

250.166 Size of the Direct- Current Grounding Elec- 
trode Conductor. The size of the grounding electrode con- 
ductor for a dc system shall be as specified in 250.166(A) 
and (B), except as permitted by 250.166(C) through (E). 

(A) Not Smaller Than the Neutral Conductor. Where the 
dc system consists of a 3-wire balancer set or a balancer wind- 
ing with overcurrent protection as provided in 445.12(D), the 
grounding electrode conductor shall not be smaller than the 
neutral conductor and not smaller than 8 AWG copper or 6 
AWG aluminum. 

(B) Not Smaller Than the Largest Conductor. Where the 
dc system is other than as in 250.166(A), the grounding 
electrode conductor shall not be smaller than the largest 
conductor supplied by the system, and not smaller than 8 
AWG copper or 6 AWG aluminum. 

(C) Connected to Rod, Pipe, or Plate Electrodes. Where 
connected to rod, pipe, or plate electrodes as in 250.52(A)(5) 
or (A)(7), that portion of the grounding electrode conductor 
that is the sole connection to the grounding electrode shall not 
be required to be larger than 6 AWG copper wire or 4 AWG 
aluminum wire. 

(D) Connected to a Concrete-Encased Electrode. Where 
connected to a concrete-encased electrode as in 250.52(A)(3), 
that portion of the grounding electrode conductor that is the 
sole connection to the grounding electrode shall not be re- 
quired to be larger than 4 AWG copper wire. 

(E) Connected to a Ground Ring. Where connected to a 
ground ring as in 250.52(A)(4), that portion of the ground- 
ing electrode conductor that is the sole connection to the 
grounding electrode shall not be required to be larger than 
the conductor used for the ground ring. 

250.168 Direct-Current System Bonding Jumper. For 

direct-current systems that are to be grounded, an unspliced 
bonding jumper shall be used to connect the equipment 
grounding conductor(s) to the grounded conductor at the 
source or the first system disconnecting means where the 
system is grounded. The size of the bonding jumper shall 
not be smaller than the system grounding electrode conduc- 
tor specified in 250.166 and shall comply with the provi- 
sions of 250.28(A), (B), and (C). 

250.169 Ungrounded Direct-Current Separately De- 
rived Systems. Except as otherwise permitted in 250.34 for 
portable and vehicle-mounted generators, an ungrounded 
dc separately derived system supplied from a stand-alone 
power source (such as an engine-generator set) shall have a 



70-128 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 250 — GROUNDING AND BONDING 



250.184 



grounding electrode conductor connected to an electrode 
that complies with Part III of this article to provide for 
grounding of metal enclosures, raceways, cables, and ex- 
posed non-current-carrying metal parts of equipment. The 
grounding electrode conductor connection shall be to the 
metal enclosure at any point on the separately derived sys- 
tem from the source to the first system disconnecting means 
or overcurrent device, or it shall be made at the source of a 
separately derived system that has no disconnecting means 
or overcurrent devices. 

The size of the grounding electrode conductor shall be 
in accordance with 250.166. 



IX. Instruments, Meters, and Relays 

250.170 Instrument Transformer Circuits. Secondary 
circuits of current and potential instrument transformers 
shall be grounded where the primary windings are con- 
nected to circuits of 300 volts or more to ground and, where 
on switchboards, shall be grounded irrespective of voltage. 

Exception No. 1: Circuits where the primary windings are 
connected to circuits of less than 1000 volts with no live 
parts or wiring exposed or accessible to other than quali- 
fied persons. 

Exception No. 2: Current transformer secondaries con- 
nected in a three-phase delta configuration shall not be 
required to be grounded. 

250.172 Instrument Transformer Cases. Cases or frames 
of instrument transformers shall be connected to the equip- 
ment grounding conductor where accessible to other than 
qualified persons. 

Exception: Cases or frames of current transformers, the 
primaries of which are not over 150 volts to ground, and 
that are used exclusively to supply current to meters. 

250.174 Cases of Instruments, Meters, and Relays Op- 
erating at Less Than 1000 Volts. Instruments, meters, and 
relays operating with windings or working parts at less than 
1000 volts shall be connected to the equipment grounding 
conductor as specified in 250.174(A), (B), or (C). 

(A) Not on Switchboards. Instruments, meters, and relays 
not located on switchboards, operating with windings or 
working parts at 300 volts or more to ground, and acces- 
sible to other than qualified persons, shall have the cases 
and other exposed metal parts connected to the equipment 
grounding conductor. 

(B) On Dead-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential trans- 
formers or connected directly in the circuit) on switchboards 
having no live parts on the front of the panels shall have the 
cases connected to the equipment grounding conductor. 



(C) On Live-Front Switchboards. Instruments, meters, 
and relays (whether operated from current and potential 
transformers or connected directly in the circuit) on switch- 
boards having exposed live parts on the front of panels 
shall not have their cases connected to the equipment 
grounding conductor. Mats of insulating rubber or other 
suitable floor insulation shall be provided for the operator 
where the voltage to ground exceeds 150. 

250.176 Cases of Instruments, Meters, and Relays — 
Operating Voltage 1 kV and Over. Where instruments, 
meters, and relays have current-carrying parts of 1 kV and 
over to ground, they shall be isolated by elevation or pro- 
tected by suitable barriers, grounded metal, or insulating 
covers or guards. Their cases shall not be connected to the 
equipment grounding conductor. 

Exception: Cases of electrostatic ground detectors where 
the internal ground segments of the instrument are con- 
nected to the instrument case and. grounded, and. the ground 
detector is isolated by elevation. 

250.178 Instrument Kquipnicnt Grounding Conductor. 

The equipment grounding conductor for secondary circuits 
of instrument transformers and for instrument cases shall 
not be smaller than 12 AWG copper or 10 AWG aluminum. 
Cases of instrument transformers, instruments, meters, and 
relays that are mounted directly on grounded metal surfaces 
of enclosures or grounded metal switchboard panels shall 
be considered to be grounded, and no additional equipment 
grounding conductor shall be required. 

X. Grounding of Systems and Circuits of over 1 kV 

250.180 General. Where systems over I kV are grounded, 
they shall comply with all applicable provisions of the preced- 
ing sections of this article and with 250.182 through 250.190, 
which supplement and modify the preceding sections. 

250.182 Derived Neutral Systems. A system neutral point 
derived from a grounding transformer shall be permitted to 
be used for grounding systems over 1 kV. 

250.184 Solidly Grounded Neutral Systems. Solidly 
grounded neutral systems shall be permitted to be either 
single point grounded or multigrounded neutral. 

(A) Neutral Conductor. 

(1) Insulation Level. The minimum insulation level for neu- 
tral conductors of solidly grounded systems shall be 600 volts. 

Exception No. 1: Bare copper conductors shall be permit- 
ted to be used for the neutral conductor of the following: 

(1) Service-entrance conductors 

(2) Service laterals 

(3) Direct-buried portions of feeders. 



2011 Edition 



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70-129 



250.186 



ARTICLE 250 — GROUNDING AND BONDING 



Exception No. 2: Bare conductors shall be permitted for 
the neutral conductor of overhead portions installed 
outdoors. 

Exception No. 3: The grounded neutral conductor shall be 
permitted to be a bare conductor if isolated from phase 
conductors and protected from physical damage. 

Informational Note: See 225.4 for conductor covering 
where within 3.0 m (10 ft) of any building or other 
structure. 

(2) Ampacity. The neutral conductor shall be of sufficient 
ampacity for the load imposed on the conductor but not less 
than 33'/? percent of the ampacity of the phase conductors. 

Exception: In industrial and commercial premises under 
engineering supervision, it shall be permissible to size the 
ampacity of the neutral conductor to not less than 20 per- 
cent of the ampacity of the phase conductor. 

(B) Single-Point Grounded Neutral System. Where a 
single-point grounded neutral system is used, the following 
shall apply: 

(1) A single-point grounded neutral system shall be permit- 
ted to be supplied from (a) or (b): 

a. A separately derived system 

b. A multigrounded neutral system with an equipment 
grounding conductor connected to the multi- 
grounded neutral conductor at the source of the 
single-point grounded neutral system 

(2) A grounding electrode shall be provided for the system. 

(3) A grounding electrode conductor shall connect the 
grounding electrode to the system neutral conductor. 

(4) A bonding jumper shall connect the equipment ground- 
ing conductor to the grounding electrode conductor. 

(5) An equipment grounding conductor shall be provided 
to each building, structure, and equipment enclosure. 

(6) A neutral conductor shall only be required where 
phase-to-neutral loads are supplied. 

(7) The neutral conductor, where provided, shall be insu- 
lated and isolated from earth except at one location. 

(8) An equipment grounding conductor shall be run with 
the phase conductors and shall comply with (a), (b), 
and (c): 

a. Shall not carry continuous load 

b. May be bare or insulated 

c. Shall have sufficient ampacity for fault current duty 

(C) Multigrounded Neutral Systems. Where a multi- 
grounded neutral system is used, the following shall apply: 
(1) The neutral conductor of a solidly grounded neutral 

system shall be permitted to be grounded at more than 
one point. Grounding shall be permitted at one or more 
of the following locations: 



a. Transformers supplying conductors to a building or 
other structure 

b. Underground circuits where the neutral conductor is 
exposed 

c. Overhead circuits installed outdoors 

(2) The multigrounded neutral conductor shall be grounded 
at each transformer and at other additional locations by 
connection to a grounding electrode. 

(3) At least one grounding electrode shall be installed and 
connected to the multigrounded neutral conductor ev- 
ery 400 m (1300 ft). 

(4) The maximum distance between any two adjacent elec- 
trodes shall not be more than 400 m (1300 ft). 

(5) In a multigrounded shielded cable system, the shielding 
shall be grounded at each cable joint that is exposed to 
personnel contact. 

250.186 Impedance Grounded Neutral Systems. Imped 
ance grounded neutral systems in which a grounding im- 
pedance, usually a resistor, limits the ground-fault current 
shall be permitted where all of the following conditions are 
met: 

(1) The conditions of maintenance and supervision ensure 
that only qualified persons service the installation. 

(2) Ground detectors are installed on the system. 

(3) Line-to-neutral loads are not served. 

Impedance grounded neutral systems shall comply with 
the provisions of 250.186(A) through (D). 

(A) Location. The grounding impedance shall be inserted 

in the grounding electrode conductor between the ground- 
ing electrode of the supply system and the neutral point of 
the supply transformer or generator. 

(B) Identified and Insulated. The neutral conductor of an 
impedance grounded neutral system shall be identified, as 
well as fully insulated with the same insulation as the phase 
conductors. 

(C) System Neutral Conductor Connection. The system 
neutral conductor shall not be connected to ground, except 
through the neutral grounding impedance. 

(D) Equipment Grounding Conductors. Equipment 
grounding conductors shall be permitted to be bare and 
shall be electrically connected to the ground bus and 
grounding electrode conductor. 

250.188 Grounding of Systems Supplying Portable or 

Mobile Equipment. Systems supplying portable or mobile 
equipment over 1 kV, other than substations installed on a 
temporary basis, shall comply with 250.188(A) through (F). 

(A) Portable or Mobile Equipment. Portable or mobile 
equipment over 1 kV shall be supplied from a system hav- 



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ARTICLE 280 — SURGE ARRESTERS, OVER 1 KV 



280.3 



ing its neutral conductor grounded through an impedance. 
Where a delta-connected system over I kV is used to sup- 
ply portable or mobile equipment, a system neutral point 
and associated neutral conductor shall be derived. 

(B) Exposed Non-Current-Carrying Metal Parts. Ex- 
posed non-current-carrying metal parts of portable or mo- 
bile equipment shall be connected by an equipment ground- 
ing conductor to the point at which the system neutral 
impedance is grounded. 

(C) Ground-Fault Current. The voltage developed be- 
tween the portable or mobile equipment frame and ground 
by the flow of maximum ground-fault current shall not 
exceed 100 volts. 

(D) Ground-Fault Detection and Relaying. Ground-fault 
detection and relaying shall be provided to automatically 

de-energize any component of a system over 1 kV that has 
developed a ground fault. The continuity of the equipment 
grounding conductor shall be continuously monitored so as 
to de-energize automatically the circuit of the system over 1 
kV to the portable or mobile equipment upon loss of con- 
tinuity of the equipment grounding conductor. 

(E) Isolation. The grounding electrode to which the por- 
table or mobile equipment system neutral impedance is 
connected shall be isolated from and separated in the 
ground by at least 6.0 m (20 ft) from any other system or 
equipment grounding electrode, and there shall be no direct 
connection between the grounding electrodes, such as bur- 
ied pipe and fence, and so forth. 

(F) Trailing Cable and Couplers. Trailing cable and cou- 
plers of systems over 1 kV for interconnection of portable 
or mobile equipment shall meet the requirements of Part III 
of Article 400 for cables and 490.55 for couplers. 

250.190 Grounding of Equipment. 

(A) Fqiiipmen G minding. All non-current-carrying metal 
parts of fixed, portable, and mobile equipment and associated 
fences, housings, enclosures, and supporting structures shall 
be grounded. 

Exception: Where isolated from ground and located such 
that any person in contact with ground cannot contact such 
metal parts when the equipment is energized, the metal 
parts shall not be reqtti cd to be grounded. 

Informational Note: See 250.110, Exception No. 2, for 
pole-mounted disnibution apparatus. 

(B) Grounding Hedrocle Conductor. If a grounding 
eneirode conduct©! connects iior-.ui;ieftt c<tn vine metal 
parts to ground, >' le grounding ele trodi conductor shall be 
sized in at cordanct w ith Table 250 66 based on the size of 
ibe largest ungrounded service, feeder. or branch-circuit 



conductors supplying the equipment The grounding elec- 
trode conductot shall no! he smallei than 6 AWG topper or 
i AWG duminum 

(C) Equipment Grounding Conductor. Equipment ground 
ing conductor! shall cofnplj with 250.190(C)(1) through 
(C)(3). 

(1) General. Equipment grounding conductors ilwt arc not 
an intejji.il part of a cal le assembly shall no! be smaller 
than 6 AWG copper or •! AWG aluminum. 

(2) ShieMcd ( ;tbV* [lie rneta lie ins ilation shield encir- 
cling the current carrying conductors shall be permitted to 
i'i* used as an riii ipment grounding conductor if it is rated 
for clearing time of groiui'l fault current protective device 
operation withoiil damaging the metallic -.be'd Tin nieinl 
lie tape "iMi'atiuii shield and drain wire insulation shield 
shall ii )1 be used as an • fiui|jifoin Hiou.j.hr-a coi/it^tor for 
iol.dl; grounded systems. 

(3) Si/by*. t'|i ipm nt grounding cortdu ton hall be sized 
in accordance v nh i, ble ->& 112 based 0,1 the current far- 
ing of the fuse or <h> oven urrenl setting 61 the protective 
relay. 

Informational Note: The overcurre-nl rating for a circuit 
breaker ■■■ the eoi tbi 1a ion ol the current transformer 1; fio 
and the i urrent pickup setting of the protective relay. 

250.191 Grounding System at Alternating-Current 
Sn!wti'ti.-nts. For ac substations the grounding system -halt 
be in accordance with Part ill ol Article 250. 

Informational Note: F01 (nunc, information on outdooi ac 
ibstatlon grounding sei ANSI/IEEE 80-2000, IEEE 
Guide fin Safit in ^L Substation C rounding 



ARTICLE 280 
Surge Arresters, Over 1 kV' 



I. General 

280.1 Scope. This article covers general requirements, instal- 
lation requirements, and connection requirements for surge 
arresters installed on premises wiring systems over 1 kV. 

280.2 Uses Not Permitted. A surge arrester shall not be 
installed where the rating of the surge arrester is less than 
the maximum continuous phase-to-ground power frequency 
voltage available at the point of application. 

280.3 Number Required. Where used at a point on a cir- 
cuit, a surge arrester shall be connected to each ungrounded 
conductor. A single installation of such surge arresters shall 



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280.4 



ARTICLE 280 — SURGE ARRESTERS, OVER 1 KV 



be permitted to protect a number of interconnected circuits, 
provided that no circuit is exposed to surges while discon- 
nected from the surge arresters. 

280.4 Surge Arrester Selection. The surge arresters shall 
comply with 280.4(A) and (B). 

(A) Rating. The rating of a surge arrester shall be equal to 
or greater than the maximum continuous operating voltage 
available at the point of application. 

(1) Solidly Grounded Systems. The maximum continuous 
operating voltage shall be the phase-to-ground voltage of 
the system. 

(2) Impedance or Ungrounded System. The maximum 
continuous operating voltage shall be the phase-to-phase 
voltage of the system. 

(B) Silicon Carbide Types. The rating of a silicon 
carbide-type surge arrester shall be not less than 125 per- 
cent of the rating specified in 280.4(A). 

Informational Note No. 1: For further information on 
surge arresters, see ANSI/IEEE C62.11-2005, Standard for 
Metal-Oxide Surge Arresters for Alternating-Current 
Power Circuits (>1 kV); and ANSI/IEEE C62.22-1997, 
Guide for the Application of Metal-Oxide Surge Arresters 
for Alternating-Current Systems. 

Informational Note No. 2: The selection of a properly 
rated metal oxide arrester is based on considerations of 
maximum continuous operating voltage and the magnitude 
and duration of overvoltages at the arrester location as af- 
fected by phase-to-ground faults, system grounding tech- 
niques, switching surges, and other causes. See the manu- 
facturer's application rules for selection of the specific 
arrester to be used at a particular location. 
■ 

II. Installation 

280.11 Location. Surge arresters shall be permitted to be 
located indoors or outdoors. Surge arresters shall be made 
inaccessible to unqualified persons, unless listed for instal- 
lation in accessible locations. 

280.12 Routing of Surge Arrester Grounding Conduc- 
tors. The conductor used to connect the surge arrester to 
line, bus, or equipment and to a grounding conductor con- 
nection point as provided in 280.21 shall not be any longer 
than necessary and shall avoid unnecessary bends. 

III. Connecting Surge Arresters 

280.21 Connection. The arrester shall be connected to one 
of the following: 

(1) Grounded service conductor 

(2) Grounding electrode conductor 



(3) Grounding electrode for the service 

(4) Equipment grounding terminal in the service equipment 

280.23 Surge-Arrester Conductors. The conductor be- 
tween the surge arrester and the line and the surge arrester 
and the grounding connection shall not be smaller than 6 
AWG copper or aluminum. 

280.24 Interconnections. The surge arrester protecting a 
transformer that supplies a secondary distribution system shall 
be interconnected as specified in 280.24(A), (B), or (C). 

(A) Metallic Interconnections. A metallic interconnection 
shall be made to the secondary grounded circuit conductor 
or the secondary circuit grounding electrode conductor pro- 
vided that, in addition to the direct grounding connection at 
the surge arrester, the following occurs: 

(1) Additional Grounding Connection. The grounded 
conductor of the secondary has elsewhere a grounding con- 
nection to a continuous metal underground water piping 
system. In urban water-pipe areas where there are at least 
four water-pipe connections on the neutral conductor and 
not fewer than four such connections in each mile of neu- 
tral conductor, the metallic interconnection shall be permit- 
ted to be made to the secondary neutral conductor with omis- 
sion of the direct grounding connection at the surge arrester. 

(2) Multigrounded Neutral System Connection. The 

grounded conductor of the secondary system is a part of a 
multigrounded neutral system or static wire of which the 
primary neutral conductor or static wire has at least four 
grounding connections in each mile of line in addition to a 
grounding connection at each service. 

(B) Through Spark Gap or Device. Where the surge ar- 
rester grounding electrode conductor is not connected as in 
280.24(A), or where the secondary is not grounded as in 
280.24(A) but is otherwise grounded as in 250.52, an inter- 
connection shall be made through a spark gap or listed 
device as required by 280.24(B)(1) or (B)(2). 

(1) Ungrounded or Unigrounded Primary System. For 

ungrounded or unigrounded primary systems, the spark gap 
or listed device shall have a 60-Hz breakdown voltage of at 
least twice the primary circuit voltage but not necessarily 
more than 10 kV, and there shall be at least one other 
ground on the grounded conductor of the secondary that is 
not less than 6.0 m (20 ft) distant from the surge-arrester 
grounding electrode. 

(2) Multigrounded Neutral Primary System. For multi- 
grounded neutral primary systems, the spark gap or listed de- 
vice shall have a 60-Hz breakdown of not more than 3 kV, and 
there shall be at least one other ground on the grounded con- 



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NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 285 — SURGE-PROTECTIVE DEVICES (SPDS), 1 KV OR LESS 



285.24 



ductor of Che secondary that is not less than 6.0 m (20 ft) 
distant from the surge-arrester grounding electrode. 

(C) By Special Permission. An interconnection of the 
surge-arrester ground and the secondary neutral conductor, 
other than as provided in 280.24(A) or (B), shall be permit- 
ted to be made only by special permission. 

280.25 Grounding Klectrode Conductor Connections 

and Enclosures. Except as indicated in this article, surge- 
arrester grounding electrode conductor connections shall be 
made as specified in Article 250, Parts III and X. Ground- 
ing electrode conductors installed in metal enclosures shall 
comply with 250.64(E). 



ARTICLE 285 

Surge-Protective Devices (SPDs), 

I kY or T ,pss 



I. General 

285.1 Scope. This article covers general requirements, in- 
stallation requirements, and connection requirements for 
SPDs [surge arresters and transient voltage surge suppres- 
sors (TVSSs)] permanently installed on premises wiring 
systems 1 kV or less. 

Informational Note No. 1: Surge arresters less than 1 kV 
are also known as Type 1 SPDs. 

Informational Note No. 2: Transient voltage surge sup- 
pressors (TVSSs) are also known as Type 2 and Type 3 
SPDs. 

285.3 Uses Not Permitted. An SPD (surge arrester or 
TVSS) device shall not be installed in the following: 

(1) Circuits exceeding 1 kV 

(2) On ungrounded systems, impedance grounded systems, 
or corner grounded delta systems unless listed specifi- 
cally for use on these systems. 

(3) Where the rating of the SPD (surge arrester or TVSS) 
is less than the maximum continuous phase-to-ground 
power frequency voltage available at the point of 
application 

Informational Note: For further information on SPDs 
(TVSSs), see NEMA LS 1-1992, Standard for Low Voltage 
Surge Suppression Devices. The selection of a properly 
rated SPD (TVSS) is based on criteria such as maximum 
continuous operating voltage, the magnitude and duration 
of overvoltages at the suppressor location as affected by 
phase-to-ground faults, system grounding techniques, and 
switching surges. 



285.4 Number Required. Where used at a point on a cir- 
cuit, the SPD (surge arrester or TVSS) shall be connected 
to each ungrounded conductor. 

285.5 Listing. An SPD (surge arrester or TVSS) shall be a 
listed device. 

285.6 Short-Circuit Current Rating. The SPD (surge ar 
rester or TVSS) shall be marked with a short-circuit current 
rating and shall not be installed at a point on the system 
where the available fault current is in excess of that rating. 
This marking requirement shall not apply to receptacles. 

II. Installation 

285.11 Location. SPDs (surge arresters or TVSSs) shall be 
permitted to be located indoors or outdoors and shall be 
made inaccessible to unqualified persons, unless listed for 
installation in accessible locations. 

285.12 Routing of Connections. The conductors used to 
connect the SPD (surge arrester or TVSS) to the line or bus 
and to ground shall not be any longer than necessary and 
shall avoid unnecessary bends. 

III. Connecting SPDs 

285.21 Connection. Where an SPD (surge arrester or TVSS) 
device is installed, it shall comply with 285.23 through 
285.28. 

285.23 Type 1 SPDs (Surge Arresters). Type 1 SPDs 
shall be installed in accordance with 285.23(A) and (B). 

(A) Installation. Type 1 SPDs (surge arresters) shall be 
installed as follows: 

(1) Type 1 SPDs (surge arresters) shall be permitted to be 
connected to the supply side of the service disconnect 
as permitted in 230.82(4) or 

(2) Type 1 SPDs (surge arresters) shall be permitted to be 
connected as specified in 285.24. 

(B) At the Service. When installed at services, Type I 
SPDs shall be connected to one of the following: 

(1) Grounded service conductor 

(2) Grounding electrode conductor 

(3) Grounding electrode for the service 

(4) Equipment grounding terminal in the service equipment 

285.24 Type 2 SPDs (TVSSs). Type 2 SPDs (TVSSs) shall 
be installed in accordance with 285.24(A) through (C). 

(A) Service-Supplied Building or Structure. Type 2 
SPDs (TVSSs) shall be connected anywhere on the load 



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285.25 



ARTICLE 285 — SURGE-PROTECTIVE DEVICES (SPDS), 1 KV OR LESS 



side of a service disconnect overcurrent device required in 
230.91, unless installed in accordance with 230.82(8). 

(B) Feeder-Supplied Building or Structure. Type 2 SPDs 
(TVSSs) shall be connected at the building or structure 
anywhere on the load side of the first overcurrent device at 
the building or structure. 

(C) Separately Derived System. The SPD (TVSS) shall 
be connected on the load side of the first overcurrent device 
in a separately derived system. 

285.25 Type 3 SPDs. Type 3 SPDs (TVSSs) shall be per- 
mitted to be installed on the load side of branch-circuit 
overcurrent protection up to the equipment served. If in- 
cluded in the manufacturer's instruc lions, the Type 3 SPD 
connection shall be a minimum 10 m (30 ft) of conductor 
distance from the service or separately derived system dis- 
connect. 



285.26 Conductor Size. Line and grounding conductors 
shall not be smaller than 14 AWG copper or 12 AWG 
aluminum. 

285.27 Connection Between Conductors. An SPD (surge 
arrester or TVSS) shall be permitted to be connected be- 
tween any two conductors — ungrounded conductor(s), 
grounded conductor, equipment grounding conductor, or 
grounding electrode conductor. The grounded conductor 
and the equipment grounding conductor shall be intercon- 
nected only by the normal operation of the SPD (surge 
arrester or TVSS) during a surge. 

285.28 Grounding Electrode Conductor Connections 
and Enclosures. Except as indicated in this article, SPD 
grounding connections shall be made as specified in Article 
250, Part III. Grounding electrode conductors installed in 
metal enclosures shall comply with 250.64(E). 



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NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 300 — WIRING METHODS 



300.3 



Chapter 3 Wiring Methods and Materials 



ARTICLE 300 
Wiring Methods 

I. General Requirements 
300.1 Scope. 

(A) AH Wiring Installations. This article covers wiring 
methods for all wiring installations unless modified by 
other articles. 

(B) Integral Parts of Equipment. The provisions of this 
article are not intended to apply to the conductors that form 
an integral part of equipment, such as motors, controllers, 
motor control centers, or factory assembled control equip- 
ment or listed utilization equipment. 

(C) Metric Designators and Trade Sizes. Metric designa- 
tors and trade sizes for conduit, tubing, and associated fittings 
and accessories shall be as designated in Table 300.1(C). 

Table 300.1(C) Metric Designators and Trade Sizes 



Metric 
Designator 



Trade 
Size 



12 

16 

21 

27 

35 

41 

53 

63 

78 

91 

103 

129 

155 



1/2 
% 
1 

1V4 

V/2 

2 

2 1/2 
3 

3 '/2 

4 
5 
6 



Note: The metric designators and trade sizes are for identification 
purposes only and are not actual dimensions. 



300.2 Limitations. 

(A) Voltage. Wiring methods specified in Chapter 3 shall 
be used for 600 volts, nominal, or less where not specifi- 
cally limited in some section of Chapter 3. They shall be 
permitted for over 600 volts, nominal, where specifically 
permitted elsewhere in this Code. 

(B) Temperature. Temperature limitation of conductors 
shall be in accordance with 310.15(A)(3). 



300.3 Conductors. 

(A) Single Conductors. Single conductors specified in 
Table 310.104(A) shall only be installed where part of a 
recognized wiring method of Chapter 3. 

Exception: Individual conductors shall be permitted 
where installed as separate overhead conductors in accor- 
dance with 225.6. 

(B) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors and bonding con- 
ductors shall be contained within the same raceway, auxil- 
iary gutter, cable tray, cablebus assembly, trench, cable, or 
cord, unless otherwise permitted in accordance with 
300.3(B)(1) through (B)(4). 

(1) Paralleled Installations. Conductors shall be permit- 
ted to be run in parallel in accordance with the provisions 
of 310.10(H). The requirement to run all circuit conductors 
within the same raceway, auxiliary gutter, cable tray, trench, 
cable, or cord shall apply separately to each portion of the 
paralleled installation, and the equipment grounding conduc- 
tors shall comply with the provisions of 250.122. Parallel runs 
in cable tray shall comply with the provisions of 392.20(C). 

Exception: Conductors installed in nonmetallic raceways 
run underground shall be permitted to be arranged as iso- 
lated phase installations. The raceways shall be installed in 
close proximity, and the conductors shall comply with the 
provisions of 300.20(B). 

(2) Grounding and Bonding Conductors. Equipment 
grounding conductors shall be permitted to be installed 
outside a raceway or cable assembly where in accor- 
dance with the provisions of 250. 1 30(C) for certain ex- 
isting installations or in accordance with 250.134(B), 
Exception No. 2, for dc circuits. Equipment bonding 
conductors shall be permitted to be installed on the out- 
side of raceways in accordance with 250.102(E). 

(3) Nonferrous Wiring Methods. Conductors in wiring 
methods with a nonmetallic or other nonmagnetic sheath, 
where run in different raceways, auxiliary gutters, cable 
trays, trenches, cables, or cords, shall comply with the pro- 
visions of 300.20(B). Conductors in single-conductor Type 
MI cable with a nonmagnetic sheath shall comply with the 
provisions of 332.31. Conductors of single-conductor Type 
MC cable with a nonmagnetic sheath shall comply with the 
provisions of 330.31, 330.116, and 300.20(B). 

(4) Enclosures. Where an auxiliary gutter runs between a 
column-width panelboard and a pull box, and the pull box 



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300.4 



ARTICLE 300 — WIRING METHODS 



includes neutral terminations, the neutral conductors of cir- 
cuits supplied from the panelboard shall be permitted to 
originate in the pull box. 

(C) Conductors of Different Systems. 

(1) 600 Volts, Nominal, or Less. Conductors of ac and dc 
circuits, rated 600 volts, nominal, or less, shall be permitted 
to occupy the same equipment wiring enclosure, cable, or 
raceway. All conductors shall have an insulation rating 
equal to at least the maximum circuit voltage applied to any 
conductor within the enclosure, cable, or raceway. 

Informational Note No. 1 : See 725.1 36(A) for Class 2 and 
Class 3 circuit conductors. 

Informational Note No. 2: See 690.4(B) for photovoltaic 
m'Iiivi." and niil|<iii i iicniK. 

(2) Over 600 Volts, Nominal. Conductors of circuits rated 
over 600 volts, nominal, shall not occupy the same equip- 
ment wiring enclosure, cable, or raceway with conductors 
of circuits rated 600 volts, nominal, or less unless otherwise 
permitted in (C)(2)(a) through (C)(2)(e). 

(a) Secondary wiring to electric-discharge lamps of 
1000 volts or less, if insulated for the secondary voltage 
involved, shall be permitted to occupy the same lumi- 
naire, sign, or outline lighting enclosure as the branch- 
circuit conductors. 

(b) Primary leads of electric-discharge lamp ballasts in- 
sulated for the primary voltage of the ballast, where con- 
tained within the individual wiring enclosure, shall be per- 
mitted to occupy the same luminaire, sign, or outline 
lighting enclosure as the branch-circuit conductors. 

(c) Excitation, control, relay, and ammeter conductors 
used in connection with any individual motor or starter 
shall be permitted to occupy the same enclosure as the 
motor-circuit conductors. 

(d) In motors, switchgear and control assemblies, and 
similar equipment, conductors of different voltage ratings 
shall be permitted. 

(e) In manholes, if the conductors of each system are 
permanently and effectively separated from the conductors 
of the other systems and securely fastened to racks, insula- 
tors, or other approved supports, conductors of different 
voltage ratings shall be permitted. 

Conductors having nonshielded insulation and operat- 
ing at different voltage levels shall not occupy the same 
enclosure, cable, or raceway. 

300.4 Protection Against Physical Damage. Where sub- 
ject to physical damage, conductors, raceways, and cables 
shall be protected. 



(A) Cables and Raceways Through Wood Members. 

(1) Bored Holes. In both exposed and concealed locations, 
where a cable- or raceway-type wiring method is installed 
through bored holes in joists, rafters, or wood members, 
holes shall be bored so that the edge of the hole is not less 
than 32 mm (] [ A in.) from the nearest edge of the wood 
member. Where this distance cannot be maintained, the 
cable or raceway shall be protected from penetration by 
screws or nails by a steel plate(s) or bushing(s), at least 
1 .6 mm ('/is in.) thick, and of appropriate length and width 
installed to cover the area of the wiring. 

Exception No. 1: Steel plates shall not be required to 
protect rigid metal conduit, intermediate metal conduit, 
rigid nonmetallic conduit, or electrical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(2) Notches in Wood. Where there is no objection because 
of weakening the building structure, in both exposed and 
concealed locations, cables or raceways shall be permitted 
to be laid in notches in wood studs, joists, rafters, or other 
wood members where the cable or raceway at those points 
is protected against nails or screws by a steel plate at least 
1.6 mm ('/i6 in.) thick, and of appropriate length and width, 
installed to cover the area of the wiring. The steel plate 
shall be installed before the building finish is applied. 

Exception No. 1: Steel plates shall not be required to 
protect rigid metal conduit, intermediate meted, conduit, 
rigid nonmetallic conduit, or electrical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(B) Nonmetallic-Sheathed Cables and Electrical Non- 
metallic Tubing Through Metal Framing Members. 

(1) Nonmetallic-Sheathed Cable. In both exposed and 
concealed locations where nonmetallic-sheathed cables pass 
through either factory- or field-punched, cut, or drilled slots or 
holes in metal members, the cable shall be protected by 
listed bushings or listed grommets covering all metal edges 
that are securely fastened in the opening prior to installa- 
tion of the cable. 

(2) Nonmetallic-Sheathed Cable and Electrical Nonme- 
tallic Tubing. Where nails or screws are likely to penetrate 
nonmetallic-sheathed cable or electrical nonmetallic tubing, 
a steel sleeve, steel plate, or steel clip not less than 1.6 mm 
(!/)6 in.) in thickness shall be used to protect the cable or 
tubing. 

Exception: A listed and marked steel plate less than 
1.6 mm (Vj6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 



70-136 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 300 — WIRING METHODS 



300.5 



(C) Cables Through Spaces Behind Panels Designed to 
Allow Access. Cables or raceway-type wiring methods, in- 
stalled behind panels designed to allow access, shall be 
supported according to their applicable articles. 

(D) Cables and Raceways Parallel to Framing Mem- 
bers and Furring Strips. In both exposed and concealed 
locations, where a cable- or raceway-type wiring method is 
installed parallel to framing members, such as joists, 
rafters, or studs, or is installed parallel to furring strips, the 
cable or raceway shall be installed and supported so that the 
nearest outside surface of the cable or raceway is not less 
than 32 mm (VA in.) from the nearest edge of the framing 
member or furring strips where nails or screws are likely to 
penetrate. Where this distance cannot be maintained, the 
cable or raceway shall be protected from penetration by 
nails or screws by a steel plate, sleeve, or equivalent at least 
1.6 mm ('/i6 in.) thick. 

Exception No. 1: Steel plates, sleeves, or the equivalent 
shall not be required to protect rigid metal conduit, inter- 
mediate metal conduit, rigid nonmetallic conduit, or elec- 
trical metallic tubing. 

Exception No. 2: For concealed work in finished build- 
ings, or finished panels for prefabricated buildings where 
such supporting is impracticable, it shall be permissible to 
fish the cables between access points. 

Exception No. 3: A listed and marked steel plate less than 
1.6 mm (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(E) Cables, Raceways, o Boxes Installed in or Under 

Roof Decking. A cable, rai e i <y, or box, installed in ex- 
posed or concealed locations under metal-corrugated sheet 
roof decking, shall be installed and supported so there is 
not less than 38 mm (l'/2 in.) measured from the h> est 
surface of the roof decking to lh fop o< Ihi- c ible i iccw i , 
or box. A cable, raceway, or box slml! not be installed in 
concealed locations in metal corrugated, ;heet decking 
type roof. 

Informational Note: Roof decking material is often re- 
paired or replaced after the initial raceway or cabling and 
roofing installation and may be penetrated by the screws or 
other mechanical devices designed to provide "hold down" 
strength of the waterproof membrane or roof insulating 
material. 

Exception: Rigid metal conduit and intermediate metal 
conduit shall not be required to comply with 300.4(E). 

(F) Cables and Raceways Installed in Shallow Grooves. 

Cable- or raceway-type wiring methods installed in a 
groove, to be covered by wallboard, siding, paneling, car- 
peting, or similar finish, shall be protected by 1.6 mm 
(!/i6 in.) thick steel plate, sleeve, or equivalent or by not 



less than 32-mm (l'/i-in.) free space for the full length of 
the groove in which the cable or raceway is installed. 

Exception No. 1: Steel plates, sleeves, or the equivalent 
shall not be required to protect rigid metal conduit, inter- 
mediate metal conduit, rigid nonmetallic conduit, or elec- 
trical metallic tubing. 

Exception No. 2: A listed and marked steel plate less than 
1.6 mm (Vi6 in.) thick that provides equal or better protec- 
tion against nail or screw penetration shall be permitted. 

(G) Insulated Fittings. Where raceways contain 4 AWG 
or larger insulated circuit conductors, and these conductors 
enter a cabinet, a box, an enclosure, or a raceway, the con- 
ductors shall be protected by an identified fitting providing 
a smoothly rounded insulating surface, unless the conduc- 
tors are separated from the fitting or raceway by identified 
insulating material that is securely fastened in place. 

Exception: Where threaded hubs or bosses that are an 
integral part of a cabinet, box, enclosure, or raceway pro- 
vide a smoothly rounded or flared entry for conductors. 

Conduit bushings constructed wholly of insulating ma- 
terial shall not be used to secure a fitting or raceway. The 
insulating fitting or insulating material shall have a tem- 
perature rating not less than the insulation temperature rat- 
ing of the installed conductors. 

(H) Structural joints. A listed expansion/deflection fitting 

or other ippre.yed mean; shuts be used where a rai :v* ij 
crosses ;i structural joint intended foi expansion, contrac 

tion ut deflection, «-k* 1 in bu Imjj'.:' brjdvt • parking ga- 
rages, oi other structures. 

300.5 Underground Installations. 

(A) Minimum Cover Requirements. Direct-buried cable 
or conduit or other raceways shall be installed to meet the 
minimum cover requirements of Table 300.5. 

(B) Wet Locations. The interior of enclosures or raceways 
installed underground shall be considered to be a wet location. 
Insulated conductors and cables installed in these enclosures 
or raceways in underground installations shall be listed for use 
in wet locations and shall comply with 310.10(C). Any con- 
nections or splices in an underground installation shall be ap- 
proved for wet locations. 

(C) Underground Cables Under Buildings. Underground 
cable installed under a building shall be in a raceway. 

Exception No. 1: Typt Wl Cat i shall be permitted undei 
a building wii'i-nd installation in a raceway where embed 
ded : ii concrete, fill o> othei masonry in accordance with 
?J2 10(6) m in underground runs where suitably protected 
against physic al damage nul • orrt y/i r < onditions m at cor 
dance with 332.10(10). 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-137 



300.5 



ARTICLE 300 — WIRING METHODS 



Table 300.5 Minimum Cover Requirements, to 600 Volts, Nominal, Burial in Millimeters (Inches) 

Type of Wiring Method or Circuit 











Column 4 


Column 5 
Circuits for 
Control of 








Column 3 


Residential 


Irrigation and 








Nonmetallic 


Branch Circuits 


Landscape 








Raceways Listed 


Rated 120 Volts or 


Lighting Limited 








for Direct Burial 


Less with GFCI 


to Not More Than 






Column 2 


Without 


Protection and 


30 Volts and 




Column 1 


Rigid Metal 


Concrete 


Maximum 


Installed with 




Direct Burial 


Conduit or 


Encasement or 


Overcurrent 


Type UF or in 




Cables or 


Intermediate 


Other Approved 


Protection of 20 


Other Identified 


Location of Wiring Method 


Conductors 


Metal Conduit 


Raceways 


Amperes 


Cable or Raceway 












or Circuit 


mm in. 


mm in. 


mm in. 


mm in. 


mm in. 


All locations not specified 


600 24 


150 6 


450 18 


300 12 


150 6 


below 












In trench below 50-mm (2-in.) 


450 18 


150 6 


300 12 


150 6 


150 6 


thick concrete or equivalent 












Under a building 



















(in raceway or 






(in raceway or 


(in raceway of 




Type MC or Type 






Type MC or Type 


Type MC or Type 




MI cable 






Ml cable identified 


Ml cable identified 




identified for 






for direct burial) ) 


for direct burial) ) 




direct burial) 










Under minimum of 102-mm 


450 1 8 


100 4 


100 4 


150 6 


150 6 


(4-in.) thick concrete exterior 












slab with no vehicular traffic 








(direct burial) 


(direct burial) 


and the slab extending not 








100 4 


100 4 


less than 152 mm (6 in.) 












beyond the underground 








(in raceway) 


(in raceway) 


installation 












Under streets, highways, roads, 


600 24 


600 24 


600 24 


600 24 


600 24 


alleys, driveways, and 












parking lots 












One- and two-family dwelling 


450 18 


450 18 


450 18 


300 12 


450 18 


driveways and outdoor 












parking areas, and used only 












for dwelling-related purposes 












In or under airport runways, 


450 18 


450 18 


450 18 


450 18 


450 18 


including adjacent areas 












where trespassing prohibited 













Notes: 

1. Cover is defined as the shortest distance in millimeters (inches) measured between a point on the top 
surface of any direct-buried conductor, cable, conduit, or other raceway and the top surface of finished grade, 
concrete, or similar cover. 

2. Raceways approved for burial only where concrete encased shall require concrete envelope not less than 
50 mm (2 in.) thick. 

3. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where 
access is otherwise required. 

4. Where one of the wiring method types listed in Columns 1-3 is used for one of the circuit types in 
Columns 4 and 5, the shallowest depth of burial shall be permitted. 

5. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be 
installed in metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a 
minimum of 50 mm (2 in.) of concrete extending down to rock. 



70-138 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 300 — WIRING METHODS 



300.6 



Exception No. 2: Type MC Cable listed for direct burial or 
concrete ericas -merit shall be permitted under •? building 
without installation in a raceway in accordance with 
33(>.l0iA)<>) ami in wet locations in aacrdancc with 
330.10(11). 

(D) Protection from Damage. Direct-buried conductors 
and cables shall be protected from damage in accordance 
with 300.5(D)(1) through (D)(4). 

(1) Emerging from Grade. Direct-buried conductors and 
cables emerging from grade and specified in columns 1 and 
4 of Table 300.5 shall be protected by enclosures or race- 
ways extending from the minimum cover distance below 
grade required by 300.5(A) to a point at least 2.5 m (8 ft) 
above finished grade. In no case shall the protection be 
required to exceed 450 mm (18 in.) below finished grade. 

(2) Conductors Entering Buildings. Conductors entering 
a building shall be protected to the point of entrance. 

(3) Service Conductors. Underground service conductors 
that are not encased in concrete and that are buried 450 mm 
(18 in.) or more below grade shall have their location iden- 
tified by a warning ribbon that is placed in the trench at 
least 300 mm (12 in.) above the underground installation. 

(4) Enclosure or Raceway Damage. Where the enclosure 
or raceway is subject to physical damage, the conductors 
shall be installed in rigid metal conduit, intermediate metal 
conduit, Schedule 80 PVC conduit, or equivalent. 

(E) Splices and Taps. Direct-buried conductors or cables 
shall be permitted to be spliced or tapped without the use of 
splice boxes. The splices or taps shall be made in accor- 
dance with 110.14(B). 

(F) Backfill. Backfill that contains large rocks, paving ma- 
terials, cinders, large or sharply angular substances, or cor- 
rosive material shall not be placed in an excavation where 
materials may damage raceways, cables, or other substruc- 
tures or prevent adequate compaction of fill or contribute to 
corrosion of raceways, cables, or other substructures. 

Where necessary to prevent physical damage to the 
raceway or cable, protection shall be provided in the form 
of granular or selected material, suitable running boards, 
suitable sleeves, or other approved means. 

(G) Raceway Seals. Conduits or raceways through which 
moisture may contact live parts shall be sealed or plugged 
at either or both ends. 

Informational Note: Presence of hazardous gases or va- 
pors may also necessitate sealing of underground conduits 
or raceways entering buildings. 

(H) Bushing. A bushing, or terminal fitting, with an inte- 
gral bushed opening shall be used at the end of a conduit or 



other raceway that terminates underground where the con- 
ductors or cables emerge as a direct burial wiring method. A 
seal incorporating the physical protection characteristics of a 
bushing shall be permitted to be used in lieu of a bushing. 

(I) Conductors of the Same Circuit. All conductors of 
the same circuit and, where used, the grounded conductor 
and all equipment grounding conductors shall be installed 
in the same raceway or cable or shall be installed in close 
proximity in the same trench. 

Exception No. 1: Conductors shall he permitted to be in- 
stalled in parallel in raceways, iiuilticonduclor tables, or 
direct-buried singk coriductot cables. Each raceway or 
multkonductot cable shall contain all conductors of the 
same circuit, including equipment grounding conductors. 
Each direct buried single conductor cable shall he located 
in , low proximity in the trench to the other sinule , ondnc- 
tor cables in tin same parallel set of conductors in the 
i in m in hiding equipme it grbundh g c onductors. 
Exception No. 2: Isolated phase, polarity, grounded con- 
ductor, and equipment grounding and bonding conductor 
installations shall be permitted in nonmetallic raceways or 
cables with a nonmetallic covering or nonmagnetic sheath 
in close proximity where conductors are paralleled as per- 
mitted in 310.10(H), and where the conditions of 300.20(B) 
are met. 

(J) Earth Movement. Where direct-buried conductors, 
raceways, or cables are subject to movement by settlement 
or frost, direct-buried conductors, raceways, or cables shall 
be arranged so as to prevent damage to the enclosed con- 
ductors or to equipment connected to the raceways. 

Informational Note: This section recognizes "S" loops in 
underground direct burial to raceway transitions, expansion 
fittings in raceway risers to fixed equipment, and, generally, 
the provision of flexible connections to equipment subject 
to settlement or frost heaves. 

(K) Directional Boring. Cables or raceways installed us- 
ing directional boring equipment shall be approved for the 
purpose. 

300.6 Protection Against Corrosion and Deterioration. 

Raceways, cable trays, cablebus, auxiliary gutters, cable 
armor, boxes, cable sheathing, cabinets, elbows, couplings, 
fittings, supports, and support hardware shall be of materials 
suitable for the environment in which they are to be installed. 

(A) Ferrous Metal Equipment. Ferrous metal raceways, 
cable trays, cablebus, auxiliary gutters, cable armor, boxes, 
cable sheathing, cabinets, metal elbows, couplings, nipples, 
fittings, supports, and support hardware shall be suitably 
protected against corrosion inside and outside (except 
threads at joints) by a coating of approved corrosion- 
resistant material. Where corrosion protection is necessary 
and the conduit is threaded in the field, the threads shall be 



201 1 Edition NATIONAL ELECTRICAL CODE 



70-139 



300.7 



ARTICLE 300 — WIRING METHODS 



coated with an approved electrically conductive, corrosion- 
resistant compound. 

Exception: Stainless steel shall not be required to have 
protective coatings. 

(1) Protected from Corrosion Solely by Enamel. Where 
protected from corrosion solely by enamel, ferrous metal 
raceways, cable trays, cablebus, auxiliary gutters, cable ar- 
mor, boxes, cable sheathing, cabinets, metal elbows, cou- 
plings, nipples, fittings, supports, and support hardware 
shall not be used outdoors or in wet locations as described 
in 300.6(D). 

(2) Organic Coatings on Boxes or Cabinets. Where boxes 
or cabinets have an approved system of organic coatings and 
are marked"Raintight," "Rainproof," or "Outdoor Type," they 
shall be permitted outdoors. 

(3) In Concrete or in Direct Contact with the Earth. 

Ferrous metal raceways, cable armor, boxes, cable sheath- 
ing, cabinets, elbows, couplings, nipples, fittings, supports, 
and support hardware shall be permitted to be installed in 
concrete or in direct contact with the earth, or in areas 
subject to severe corrosive influences where made of mate- 
rial approved for the condition, or where provided with 
corrosion protection approved for the condition. 

(B) Aluminum Metal Equipment. Aluminum raceways, 
cable trays, cablebus, auxiliary gutters, cable armor, boxes, 
cable sheathing, cabinets, elbows, couplings, nipples, fittings, 
supports, and support hardware embedded or encased in con- 
crete or in direct contact with the earth shall be provided with 
supplementary corrosion protection. 

(C) Nonmetallic Equipment. Nonmetallic raceways, cable 
trays, cablebus, auxiliary gutters, boxes, cables with a non- 
metallic outer jacket and internal metal armor or jacket, 
cable sheathing, cabinets, elbows, couplings, nipples, fit- 
tings, supports, and support hardware shall be made of ma- 
terial approved for the condition and shall comply with 
(C)(1) and (C)(2) as applicable to the specific installation. 

(1) Exposed to Sunlight. Where exposed to sunlight, the 
materials shall be listed as sunlight resistant or shall be 
identified as sunlight resistant. 

(2) Chemical Exposure. Where subject to exposure to 
chemical solvents, vapors, splashing, or immersion, materials 
or coatings shall either be inherently resistant to chemicals 
based on their listing or be identified for the specific chemical 
reagent. 

(D) Indoor Wet Locations. In portions of dairy processing 
facilities, laundries, canneries, and other indoor wet loca- 
tions, and in locations where walls are frequently washed or 
where there are surfaces of absorbent materials, such as 
damp paper or wood, the entire wiring system, where in- 



stalled exposed, including all boxes, fittings, raceways, and 
cable used therewith, shall be mounted so that there is at 
least a 6-mm (Vi-in.) airspace between it and the wall or 
supporting surface. 

Exception: Nonmetallic raceways, boxes, and fittings shall 
be permitted to be installed without the airspace on a con- 
crete, masonry, tile, or similar surface. 

Informational Note: In general, areas where acids and al- 
kali chemicals are handled and stored may present such 
corrosive conditions, particularly when wet or damp. Se- 
vere corrosive conditions may also be present in portions of 
meatpacking plants, tanneries, glue houses, and some 
stables; in installations immediately adjacent to a seashore 
and swimming pool areas; in areas where chemical deicers 
are used; and in storage cellars or rooms for hides, casings, 
fertilizer, salt, and bulk chemicals. 

300.7 Raceways Exposed to Different Temperatures. 

(A) Sealing. Where portions of a raceway or sleeve are 
known to be subjected to different temperatures, and where 
condensation is known to be a problem, as in cold storage 
areas of buildings or where passing from the interior to the 
exterior of a building, the raceway or sleeve shall be filled 
with an approved material to prevent the circulation of 
warm air to a colder section of the raceway or sleeve. An 
explosionproof seal shall not be required for this purpose. 

(B) Expansion Fittings. Raceways shall be provided with 
expansion fittings where necessary to compensate for ther- 
mal expansion and contraction. 

Informational Note: Table 352.44 and Table 355.44 pro- 
vide the expansion information for polyvinyl chloride 
(PVC) and for reinforced thermosetting resin conduit 
(RTRC), respectively. A nominal number for steel conduit 
can be determined by multiplying the expansion length in 
Table 352.44 by 0.20. The coefficient of expansion for steel 
electrical metallic tubing, intermediate metal conduit, and 
rigid conduit is 1.170x lO -5 (0.0000117 mm per mm of 
conduit for each °C in temperature change) [0.650 x 10~ 5 
(0.0000065 in. per inch of conduit for each °F in tempera- 
ture change)]. 

A nominal number for aluminum conduit and alumi- 
num electrical metallic tubing can be determined by multi- 
plying the expansion length in Table 352.44 by 0.40. The 
coefficient of expansion for aluminum electrical metallic 
tubing and aluminum rigid metal conduit is 2.34 x 10~ 5 
(0.0000234 mm per mm of conduit for each °C in tempera- 
ture change) [1.30 x 10" 5 (0.000013) in. per inch of conduit 
for each °F in temperature change). 

300.8 Installation of Conductors with Other Systems. 

Raceways or cable trays containing electrical conductors 
shall not contain any pipe, tube, or equal for steam, water, 
air, gas, drainage, or any service other than electrical. 

300.9 Raceways in Wet Locations Abovegrade. Where 
raceways are installed in wet locations abovegrade, the interior 



70-140 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 300 — WIRING METHODS 



300.13 



of these raceways shall be considered to be a wet location. 
Insulated conductors and cables installed in raceways in wet 
locations abovegrade shall comply with 310.10(C). 

300.10 Electrical Continuity of Metal Raceways and 
Enclosures. Metal raceways, cable armor, and other metal 
enclosures for conductors shall be metallically joined to- 
gether into a continuous electrical conductor and shall be 
connected to all boxes, fittings, and cabinets so as to pro- 
vide effective electrical continuity. Unless specifically per- 
mitted elsewhere in this Code, raceways and cable assem- 
blies shall be mechanically secured to boxes, fittings, 
cabinets, and other enclosures. 

Exception No. 1: Short sections of raceways used to pro- 
vide support or protection of cable assemblies from physi- 
cal damage shall not be required to be made electrically 
continuous. 

Exception No. 2: Equipment enclosures to be isolated, as 
permitted by 250.96(B), shall not be required to be metal- 
lically joined to the metal raceway. 

300.11 Securing and Supporting. 

(A) Secured in Place. Raceways, cable assemblies, boxes, 
cabinets, and fittings shall be securely fastened in place. 
Support wires that do not provide secure support shall not 
be permitted as the sole support. Support wires and associ- 
ated fittings that provide secure support and that are in- 
stalled in addition to the ceiling grid support wires shall be 
permitted as the sole support. Where independent support 
wires are used, they shall be secured at both ends. Cables 
and raceways shall not be supported by ceiling grids. 

(1) Fire-Rated Assemblies. Wiring located within the cav- 
ity of a fire-rated floor-ceiling or roof-ceiling assembly 
shall not be secured to, or supported by, the ceiling assem- 
bly, including the ceiling support wires. An independent 
means of secure support shall be provided and shall be 
permitted to be attached to the assembly. Where indepen- 
dent support wires are used, they shall be distinguishable 
by color, tagging, or other effective means from those that 
are part of the fire-rated design. 

Exception: The ceiling support system shall be permitted 
to support wiring and equipment that have been tested as 
part of the fire-rated assembly. 

Informational Note: One method of determining fire rating 
is testing in accordance with NFPA 251-2006, Standard 
Methods of Tests of Fire Resistance of Building Construc- 
tion and Materials. 

(2) Non-Fire-Rated Assemblies. Wiring located within 
the cavity of a non-fire-rated floor-ceiling or roof-ceiling 
assembly shall not be secured to, or supported by, the ceil- 
ing assembly, including the ceiling support wires. An inde- 
pendent means of secure support shall be provided and 



shall be permitted to be attached to the assembly. Where 
independent support wires are used, they shall be distin- 
guishable by color, tagging, or othei effective means. 

Exception: The ceiling support system shall be permitted 
to support branch-circuit wiring and associated equipment 
where installed in accordance with the ceiling system 
manufacturer 's instructions. 

(B) Raceways Used as Means of Support. Raceways 
shall be used only as a means of support for other race- 
ways, cables, or nonelectrical equipment under any of the 
following conditions: 

(1) Where the raceway or means of support is identified for 
the purpose 

(2) Where the raceway contains power supply conductors 
for electrically controlled equipment and is used to sup- 
port Class 2 circuit conductors or cables that are solely 
for the purpose of connection to the equipment control 
circuits 

(3) Where the raceway is used to support boxes or conduit 
bodies in accordance with 314.23 or to support lumi- 
naires in accordance with 410.36(E) 

(C) Cables Not Used as Means of Support. Cable wiring 
methods shall not be used as a means of support for other 
cables, raceways, or nonelectrical equipment. 

300.12 Mechanical Continuity — Raceways and Cables. 

Metal or nonmetallic raceways, cable armors, and cable 
sheaths shall be continuous between cabinets, boxes, fit- 
tings, or other enclosures or outlets. 

Exception No. I: Short sections of raceways used to pro- 
vide support or protection of cable assemblies from physi- 
cal damage shall not be required to be mechanically 
continuous. 

Exception No. 2: Raceways and cables installed into the 
bottom of open bottom equipment, such as switchboards, 
motor control centers, and floor or pad-mounted transform- 
ers, shall not be required to be mechanically secured to the 
equipment. 



300.13 Mechanical and Electrical Continuity 
ductors. 



Con- 



(A) General. Conductors in raceways shall be continuous 
between outlets, boxes, devices, and so forth. There shall be 
no splice or tap within a raceway unless permitted by 300.15; 
368.56(A); 376.56; 378.56; 384.56; 386.56; 388.56; or 390.7. 

(B) Device Removal. In multiwire branch circuits, the 
continuity of a grounded conductor shall not depend on 
device connections such as lampholders, receptacles, and 
so forth, where the removal of such devices would interrupt 
the continuity. 



2011 Edition NATIONAL ELECTRICAL CODE 



70-141 



300.14 



ARTICLE 300 — WIRING METHODS 



300.14 Length of Free Conductors at Outlets, Junc- 
tions, and Switch Points. At least 150 mm (6 in.) of free 
conductor, measured from the point in the box where it 
emerges from its raceway or cable sheath, shall be left at each 
outlet, junction, and switch point for splices or the connection 
of luminaires or devices. Where the opening to an outlet, junc- 
tion, or switch point is less than 200 mm (8 in.) in any dimen- 
sion, each conductor shall be long enough to extend at least 
75 mm (3 in.) outside the opening. 

Exception: Conductors that are not spliced or terminated 
at the outlet, junction, or switch point shall not be required 
to comply with 300.14. 

300.15 Boxes, Conduit Bodies, or Fittings — Where Re- 
quired. A box shall be installed at each outlet and switch 
point for concealed knob-and-tube wiring. 

Fittings and connectors shall be used only with the spe- 
cific wiring methods for which they are designed and listed. 

Where the wiring method is conduit, tubing, Type AC 
cable, Type MC cable, Type MI cable, nonmetallic-sheathed 
cable, or other cables, a box or conduit body shall be installed 
at each conductor splice point, outlet point, switch point, junc- 
tion point, termination point, or pull point, unless otherwise 
permitted in 300.15(A) through (L). 

(A) Wiring Methods with Interior Access. A box or con- 
duit body shall not be required for each splice, junction, 
switch, pull, termination, or outlet points in wiring methods 
with removable covers, such as wireways, multioutlet as- 
semblies, auxiliary gutters, and surface raceways. The cov- 
ers shall be accessible after installation. 

(B) Equipment. An integral junction box or wiring com- 
partment as part of approved equipment shall be permitted 
in lieu of a box. 

(C) Protection. A box or conduit body shall not be re- 
quired where cables enter or exit from conduit or tubing 
that is used to provide cable support or protection against 
physical damage. A fitting shall be provided on the end(s) 
of the conduit or tubing to protect the cable from abrasion. 

(D) Type MI Cable. A box or conduit body shall not be 
required where accessible fittings are used for straight- 
through splices in mineral-insulated metal-sheathed cable. 

(E) Integral Enclosure. A wiring device with integral en- 
closure identified for the use, having brackets that securely 
fasten the device to walls or ceilings of conventional on- 
site frame construction, for use with nonmetallic-sheathed 
cable, shall be permitted in lieu of a box or conduit body. 

Informational Note: See 334.30(C); 545.10; 550.15(1); 
551.47(E), Exception No. 1; and 552.48(E), Exception No. 1. 

(F) Fitting. A fitting identified for the use shall be permit- 
ted in lieu of a box or conduit body where conductors are 



not spliced or terminated within the fitting. The fitting shall 
be accessible after installation. 

(G) Direct-Buried Conductors. As permitted in 300.5(E), 
a box or conduit body shall not be required for splices and 
taps in direct-buried conductors and cables. 

(H) Insulated Devices. As permitted in 334.40(B), a box 
or conduit body shall not be required for insulated devices 
supplied by nonmetallic-sheathed cable. 

(I) Enclosures. A box or conduit body shall not be required 
where a splice, switch, terminal, or pull point is in a cabinet or 
cutout box, in an enclosure for a switch or overcurrent device 
as permitted in 312.8, in a motor controller as permitted in 
430.10(A), or in a motor control center. 

(J) Luminaires. A box or conduit body shall not be required 
where a luminaire is used as a raceway as permitted in 410.64, 

(K) Embedded. A box or conduit body shall not be required 
for splices where conductors are embedded as permitted in 

424.40, 424.41(D), 426.22(B), 426.24(A), and 427.19(A). 

(L) Manholes and Handhole Enclosures. A box or con- 
duit body shall not be required for conductors in manholes 
or handhole enclosures, except where connecting to electri- 
cal equipment. The installation shall comply with the pro- 
visions of Part V of Article 110 for manholes, and 314.30 
for handhole enclosures. 

300.16 Raceway or Cable to Open or Concealed Wiring. 

(A) Box, Conduit Body, or Fitting. A box, conduit body, 
or terminal fitting having a separately bushed hole for each 
conductor shall be used wherever a change is made from 
conduit, electrical metallic tubing, electrical nonmetallic 
tubing, nonmetallic-sheathed cable, Type AC cable, Type 
MC cable, or mineral-insulated, metal-sheathed cable and 
surface raceway wiring to open wiring or to concealed 
knob-and-tube wiring. A fitting used for this purpose shall 
contain no taps or splices and shall not be used at luminaire 
outlets. A conduit body used for this purpose shall contain 
no taps or splices, unless it complies with 314.16(C)(2). 

(B) Bushing. A bushing shall be permitted in lieu of a box 
or terminal where the conductors emerge from a raceway 
and enter or terminate at equipment, such as open switch- 
boards, unenclosed control equipment, or similar equip- 
ment. The bushing shall be of the insulating type for other 
than lead-sheathed conductors. 

300.17 Number and Size of Conductors in Raceway. 

The number and size of conductors in any raceway shall 
not be more than will permit dissipation of the heat and 
ready installation or withdrawal of the conductors without 
damage to the conductors or to their insulation. 



70-142 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 300 — WIRING METHODS 



300.19 



Informational Note: See the following sections of this 
Code: intermediate metal conduit, 342.22; rigid metal con- 
duit, 344.22; flexible metal conduit, 348.22; liquidtight 
flexible metal conduit, 350.22; PVC conduit, 352.22; 
HDPE conduit, 353.22; RTRC, 355.22; liquidtight nonme- 
tallic flexible conduit, 356.22; electrical metallic tubing, 
358.22; flexible metallic tubing, 360.22; electrical nonme- 
tallic tubing, 362.22; cellular concrete floor raceways, 
372.11; cellular metal floor raceways, 374.5; metal wire- 
ways, 376.22; nonmetallic wireways, 378.22; surface metal 
raceways, 386.22; surface nonmetallic raceways, 388.22; 
underfloor raceways, 390.6; fixture wire, 402.7; theaters, 
520.6; signs, 600.31(C); elevators, 620.33; audio signal 
processing, amplification, and reproduction equipment, 
640.23(A) and 640.24; Class 1, Class 2, and Class 3 cir- 
cuits, Article 725; fire alarm circuits, Article 760; and opti- 
cal fiber cables and raceways, Article 770. 

300.18 Raceway Installations. 

(A) Complete Runs. Raceways, other than busways or ex- 
posed raceways having hinged or removable covers, shall be 
installed complete between outlet, junction, or splicing points 
prior to the installation of conductors. Where required to fa- 
cilitate the installation of utilization equipment, the raceway 
shall be permitted to be initially installed without a terminat- 
ing connection at the equipment. Prewired raceway assemblies 
shall be permitted only where specifically permitted in this 
Code for the applicable wiring method. 

Exception: Short sections of raceways used to contain 
conductors or cable assemblies for protection from physi- 
cal damage shall not be required to be installed complete 
between outlet, junction, or splicing points. 

(B) Welding. Metal raceways shall not be supported, ter- 
minated, or connected by welding to the raceway unless 
specifically designed to be or otherwise specifically permit- 
ted to be in this Code. 



300.19 Supporting Conductors in Vertical Raceways. 

(A) Spacing Intervals — Maximum. Conductors in ver- 
tical raceways shall be supported if the vertical rise exceeds 
the values in Table 300.19(A). One cable support shall be 
provided at the top of the vertical raceway or as close to the 
top as practical. Intermediate supports shall be provided as 
necessary to limit supported conductor lengths to not 
greater than those values specified in Table 300.19(A). 

Exception: Steel wire armor cable shall be supported at 
the top of the riser with a cable support that clamps the 
steel wire armor. A safety device shall be permitted at the 
lower end of the riser to hold the cable in the event there is 
slippage of the cable in the wire-armored cable support. 
Additional wedge-type supports shall be permitted to re- 
lieve the strain on the equipment terminals caused by ex- 
pansion of the cable under load. 

(B) Fire-Rated Cables and Conductors. Support meth- 
ods and spacing intervals for fire-rated cables and conduc- 
tors shall comply with any restrictions provided in the list- 
ing of the electrical circuit protective system used and in no 
case shall exceed the values in Table 300.19(A). 

(C) Support Methods. One of the following methods of 
support shall be used: 

(1) By clamping devices constructed of or employing insu- 
lating wedges inserted in the ends of the raceways. 
Where clamping of insulation does not adequately sup- 
port the cable, the conductor also shall be clamped. 

(2) By inserting boxes at the required intervals in which in- 
sulating supports are installed and secured in a satisfac- 
tory manner to withstand the weight of the conductors 
attached thereto, the boxes being provided with covers. 



Table 300.19(A) Spacings for Conductor Supports 











Conductors 










Support of 

Conductors in 

Vertical 

Raceways 




Aluminum oi 

Copper- Clad 

Aluminum 






Copper 




Conductor Size 


m 




ft 


in 




ft 


18 AWG through 8 AWG 
6 AWG through 1/0 AWG 
2/0 AWG through 4/0 AWG 
Over 4/0 AWG through 350 kcmil 
Over 350 kcmil through 500 kcmil 
Over 500 kcmil through 750 kcmil 
Over 750 kcmil 


Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 
Not greater than 


30 
60 
55 
41 
36 
28 
26 




100 
200 
180 
135 
120 
95 
85 


30 
30 
25 
18 
15 
12 
11 




100 
100 
80 
60 
50 
40 
35 


201 1 Edition NATIONAL ELECTRICAL CODE 












70-143 



300.20 



ARTICLE 300 — WIRING METHODS 



(3) In junction boxes, by deflecting the cables not less than 
90 degrees and carrying them horizontally to a distance 
not less than twice the diameter of the cable, the cables 
being carried on two or more insulating supports and 
additionally secured thereto by tie wires if desired. 
Where this method is used, cables shall be supported at 
intervals not greater than 20 percent of those mentioned 
in the preceding tabulation. 

(4) By a method of equal effectiveness. 

300.20 Induced Currents in Ferrous Metal Enclosures 
or Ferrous Metal Raceways. 

(A) Conductors Grouped Together. Where conductors 
carrying alternating current are installed in ferrous metal 
enclosures or ferrous metal raceways, they shall be ar- 
ranged so as to avoid heating the surrounding ferrous metal 
by induction. To accomplish this, all phase conductors and, 
where used, the grounded conductor and all equipment 
grounding conductors shall be grouped together. 

Exception No. I: Equipment grounding conductors for 
certain existing installations shall be permitted to be in- 
stalled separate from their associated circuit conductors 
where run in accordance with the provisions of 250.130(C). 

Exception No. 2: A single conductor shall be permitted to 
be installed in a ferromagnetic enclosure and used for skin- 
effect heating in accordance with the provisions of 426.42 
and 427.47. 

(B) Individual Conductors. Where a single conductor 
carrying alternating current passes through metal with mag- 
netic properties, the inductive effect shall be minimized by 
(1) cutting slots in the metal between the individual holes 
through which the individual conductors pass or (2) passing 
all the conductors in the circuit through an insulating wall 
sufficiently large for all of the conductors of the circuit. 

Exception: In the case of circuits supplying vacuum or 
electric-discharge lighting systems or signs or X-ray appara- 
tus, the currents carried by the conductors are so small that 
the inductive heating effect can be ignored where these con- 
ductors are placed in metal enclosures or pass through metal. 

Informational Note: Because aluminum is not a magnetic 
metal, there will be no heating due to hysteresis; however, 
induced currents will be present. They will not be of suffi- 
cient magnitude to require grouping of conductors or spe- 
cial treatment in passing conductors through aluminum 
wall sections. 

300.21 Spread of Fire or Products of Combustion. Elec- 
trical installations in hollow spaces, vertical shafts, and 
ventilation or air-handling ducts shall be made so that the 
possible spread of fire or products of combustion will not 
be substantially increased. Openings around electrical pen- 
etrations into or through fire-resistant-rated walls, parti- 



tions, floors, or ceilings shall be firestopped using approved 
methods to maintain the fire resistance rating. 

Informational Note: Directories of electrical construction 
materials published by qualified testing laboratories contain 
many listing installation restrictions necessary to maintain 
the fire-resistive rating of assemblies where penetrations or 
openings are made. Building codes also contain restrictions 
on membrane penetrations on opposite sides of a fire- 
resistance-rated wall assembly. An example is the 600-mm 
(24-in.) minimum horizontal separation that usually applies 
between boxes installed on opposite sides of the wall. As- 
sistance in complying with 300.21 can be found in building 
codes, fire resistance directories, and product listings. 

300.22 Wiring in Ducts Not Used lor Air Handling, 
Fabricated Ducts for Environmental Air, and Other 
Spaces for Environment;:? \ii (Plenums). The provisions 
of this section shall apply to the installation and uses of 
electrical wiring and equipment in ducts used for dust, 
loose stock, or vapor removal: ducts specifically fabricated 
for environmental air: and other spaces used for environ- 
mental air (plenums). 

Informational Note: See Article 424, Part VI, for duct 
heaters. 

(A) Ducts for Dust, Loose Stock, or Vapor Removal. No 

wiring systems of any type shall be installed in ducts used 
to transport dust, loose stock, or flammable vapors. No 
wiring system of any type shall be installed in any duct, or 
shaft containing only such ducts, used for vapor removal or 
for ventilation of commercial-type cooking equipment. 

(B) Ducts Specifically Fabricated for Environmental Air. 

Only wiring methods consisting of Type MI cable, Type 
MC cable employing a smooth or corrugated impervious 
metal sheath without an overall nonmetallic covering, elec- 
trical metallic tubing, flexible metallic tubing, intermediate 
metal conduit, or rigid metal conduit without an overall 
nonmetallic covering shall be installed in ducts specifically 
fabricated to transport environmental air. Flexible metal 
conduit shall be permitted, in lengths not to exceed 1 .2 m 
(4 ft), to connect physically adjustable equipment and de- 
vices permitted to be in these fabricated ducts. The connec- 
tors used with flexible metal conduit shall effectively close 
any openings in the connection. Equipment and devices 
shall be permitted within such ducts only if necessary for 
the direct action upon, or sensing of, the contained air. 
Where equipment or devices are installed and illumination 
is necessary to facilitate maintenance and repair, enclosed 
gasketed-type luminaires shall be permitted. 

(C) Other Spaces Used for Environmental Air (Ple- 
nums). This section shall apply to spaces not specifically 
fabricated for environmental air-handling purposes but used 
for air-handling purposes as a plenum. This section shall 



70-144 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 300 — WIRING METHODS 



300.39 



not apply to habitable rooms or areas of buildings, the 
prime purpose of which is not air handling. 

Informational Note No. 1 : The space over a hung ceiling 
used for environmental air-handling purposes is an example 
of the type of other space to which this section applies. 

Informational Note No. 2: The hrasi Other Spaces Used 
foi Em onmental Vii (PI num.) is used u, this section 
correlate; -Mil' i u use of <L i rm plenum" i>> i > PA )0 \ 
JO 19 Stan U rd foi r ',c Install < »< o) Au & •■'1<u mu g md 
Ventilating Sys < wis and other in nanicr.l codes where the 
pleni m ( a ed for tuui> jo ,'>iq>^.i r , as • i m as some 
othei air-h indling sp tees 

Exception: This section shall not apply to the joist or stud 
spaces of dwelling units where the wiring passes through 
such spaces perpendicular to the long dimension of such 
spaces. 

(1) Wiring Methods. The wiring methods for such other 
space shall be limited to totally enclosed, nonventilated, 
insulated busway having no provisions for plug-in connec- 
tions, Type MI cable, Type MC cable without an overall 
nonmetallic covering, Type AC cable, or other factory- 
assembled multiconductor control or power cable that is 
specifically listed for use within an air-handling space, or 
listed prefabricated cable assemblies of metallic manufac- 
tured wiring systems without nonmetallic sheath. Other 
types of cables, conductors, and raceways shall be permit- 
ted to be installed in electrical metallic tubing, flexible me- 
tallic tubing, intermediate metal conduit, rigid metal con- 
duit without an overall nonmetallic covering, flexible metal 
conduit, or, where accessible, surface metal raceway or 
metal wireway with metal covers. 

(2) Cable Tray Systems. The provisions in (a) or (b) shall 
apply to the use of metallic cable tray systems in other 
Space . used for r.ivir<>mn«nt 1 ai (plenums), where acces- 
sible, as follows: 

(a) Metal Cable Tray Systems. Metal cable tray sys- 
tems shall be permitted to support the wiring mediods in 
300.22(C)(1). 

(b) Solid Side and Bottom Metal Cabh fray Systems. 
Solid side and b.jff-wi moid cable traj systems with solid 
tCklrJ • overs shall hi perm i Me I 'o enclosi tvirl i<: mcirn -is 
and cables, not alread) co> s red in 300.22(C )(1 s. in accor- 
dance with 392.10(A) and (B). 

(3) Equipment. Electrical equipment with a metal enclo- 
sure, or electrical equipment with a nonmetallic enclosure 
listed for use within .o -m-h in lling space and having ad- 
equate fire-resistant and low-smoke-producing characteris- 
tics, and associated wiring material suitable for the ambient 
temperature shall be permitted to be installed in such other 
space unless prohibited elsewhere in this Code. 

Informational Note: One method of defining adequate 
iiie r- M,tnnf and lew n</k.e produ ine il tracts v ti< foi 



electrical equipmen wth a nonmetallic enclosure is in 
ANSI/DL : 20f 3-200!: Fit Test far Heat and Visibh Smoke 
Release for Discrete Products and Their Accessories In- 
stalled in Air-Hiiiiillinti .S'/v. t -. 

Exception: Integral fan systems shall be permitted where 
specifically identified for use within an air-handling space. 

(D) Information Technology Equipment. Electrical wir- 
ing in air-handling areas beneath raised floors for informa- 
tion technology equipment shall be permitted in accordance 
with Article 645. 

300.23 Panels Designed to Allow Access. Cables, race- 
ways, and equipment installed behind panels designed to 
allow access, including suspended ceiling panels, shall be 
arranged and secured so as to allow the removal of panels 
and access to the equipment. 

II. Requirements for over 600 Volts, Nominal 

300.31 Covers Required. Suitable covers shall be installed 
on all boxes, fittings, and similar enclosures to prevent acci- 
dental contact with energized parts or physical damage to parts 
or insulation. 

300.32 Conductors of Different Systems. See 300.3(C)(2). 

300.34 Conductor Bending Radius. The conductor shall 
not be bent to a radius less than 8 times the overall diameter 
for nonshielded conductors or 12 times the overall diameter 
for shielded or lead-covered conductors during or after instal- 
lation. For multiconductor or multiplexed single-conductor 
cables having individually shielded conductors, the minimum 
bending radius is 12 times the diameter of the individually 
shielded conductors or 7 times the overall diameter, whichever 
is greater. 

300.35 Protection Against Induction Heating. Metallic 
raceways and associated conductors shall be arranged so as 
to avoid heating of the raceway in accordance with the 
applicable provisions of 300.20. 

300.37 Aboveground Wiring Methods. Aboveground con- 
ductors shall be installed in rigid metal conduit, in intermedi- 
ate metal conduit, in electrical metallic tubing, in RTRC and 
PVC conduit, in cable trays, in auxiliary gutters, as busways, 
as cablebus, in other identified raceways, or as exposed 
runs of metal-clad cable suitable for the use and purpose. In 
locations accessible to qualified persons only, exposed runs 
of Type MV cables, bare conductors, and bare busbars shall 
also be permitted. Busbars shall be permitted to be either 
copper or aluminum. 

300.39 Braid-Covered Insulated Conductors — Ex- 
posed Installation. Exposed runs of braid-covered insu- 
lated conductors shall have a flame-retardant braid. If the 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-145 



300.40 



ARTICLE 300 — WIRING METHODS 



conductors used do not have this protection, a flame- 
retardant saturant shall be applied to the braid covering 
after installation. This treated braid covering shall be 
stripped back a safe distance at conductor terminals, ac- 
cording to the operating voltage. Where practicable, this 
distance shall not be less than 25 mm (1 in.) for each 
kilovolt of the conductor-to-ground voltage of the circuit. 

300.40 Insulation Shielding. Metallic and semiconducting 
insulation shielding components of shielded cables shall be 
removed for a distance dependent on the circuit voltage and 
insulation. Stress reduction means shall be provided at all 
terminations of factory-applied shielding. 

Metallic shielding components such as tapes, wires, or 
braids, or combinations thereof, shall be connected to a 
grounding conductor, grounding busbar, or a grounding 
electrode. 



300.42 Moisture or Mechanical Protection for Metal - 
Sheathed Cables. Where cable conductors emerge from a 
metal sheath and where protection against moisture or 
physical damage is necessary, the insulation of the conduc- 
tors shall be protected by a cable sheath terminating device. 

300.50 Underground Installations. 

(A) General. Underground conductors shall be identified 
for the voltage and conditions under which they are in- 
stalled. Direct-burial cables shall comply with the provi- 
sions of 310.10(F). Underground cables shall be installed in 
accordance with 300.50(A)(1) or (A)(2), and the installa- 
tion shall meet the depth requirements of Table 300.50. 

(1) Shielded Cables and Nonshielded Cables in Metal- 
Sheathed Cable Assemblies. Underground cables, including 



Table 300.50 Minimum Cover" Requirements 





General Conditions (not otherwise specified) 


Special Conditions (use if applicable) 




Column I 


Column 2 


Column 3 


Column 4 


Column 5 


Column 6 




Direct-Buried 
Cables" 


rtrc, rvc, 

and HDPK 
Conduit 1 ' 


Rigid Metal 

Conduit and 

Intermediate 

Metal Conduit 


Raceways 

Under 

Buildings or 

Exterior 

Concrete 

Slabs, 100 mm 

(4 in.) 

Minimum 

Thickness c 


Cables in 

Airport 

Runways or 

Adjacent 

Areas Where 

Trespass Is 

Prohibited 


Areas Subject to 
Vehicular Traffic, 

Such as 

Thoroughfares and 

Commercial Parking 

Areas 


Circuit Voltage 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


mm 


in. 


Over 600 V 
through 22 kV 


750 


30 


450 


18 


150 


6 


100 


4 


450 


18 


600 


24 


Over 22 kV 
through 40 kV 


900 


36 


600 


24 


150 


6 


100 


4 


450 


18 


600 


24 


Over 40 kV 


1000 


42 


750 


30 


150 


6 


100 


4 


450 


18 


600 


24 



General Notes: 

1. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required. 

2. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway 
permitted for direct burial. The raceways shall be covered by a minimum of 50 mm (2 in.) of concrete extending down to rock. 

3. In industrial establishments, where conditions of maintenance and supervision ensure that qualified persons will service the installation, the 
minimum cover requirements, for other than rigid metal conduit and intermediate metal conduit, shall be permitted to be reduced 150 mm (6 in.) 
for each 50 mm (2 in.) of concrete or equivalent placed entirely within the trench over the underground installation. 

Specific Footnotes: 

a Cover is defined as the shortest distance in millimeters (inches) measured between a point on the top surface of any direct-buried conductor, cable, 

conduit, or other raceway and the top surface of finished grade, concrete, or similar cover. 

b Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm (2 in.) 

of concrete or equivalent above conduit in addition to the table depth. 

c The slab shall extend a minimum of 150 mm (6 in.) beyond the underground installation, and a warning ribbon or other effective means suitable 

for the conditions shall be placed above the underground installation. 

d Underground direct-buried cables that are not encased or protected by concrete and are buried 750 mm (30 in.) or more below grade shall have 

their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the cables. 



70-146 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.10 



nonshielded, Type MC and moisture-impervious metal sheath 
cables, shall have those sheaths grounded through an effective 
grounding path meeting the requirements of 250.4(A)(5) or 
(B)(4). They shall be direct buried or installed in raceways 
identified for the use. 

(2) Other Nonshielded Cables. Other nonshielded cables 
not covered in 300.50(A)(1) shall be installed in rigid metal 
conduit, intermediate metal conduit, or rigid nonmetallic 
conduit encased in not less than 75 mm (3 in.) of concrete. 

(B) Wet Locations. The interior of i ik lo in ;s o raceways 
installed underground shall he considered to be a wet loca- 
tion. Insulated conductors and cable installed in these en- 
closures or raceways in undergi mini installations shali bt. 
listed for use in wet locations and shall comply with 
310.10(C). Any connections or spikes in an underground 
installation shall be approved for wet locations. 

(C) Protection from Damage. Conductors emerging from 
the ground shall be enclosed in listed raceways. Raceways 
installed on poles shall be of rigid metal conduit, interme- 
diate metal conduit, RTRC-XW, Schedule 80 PVC conduit, 
or equivalent, extending from the minimum cover depth 
specified in Table 300.50 to a point 2.5 m (8 ft) above finished 
grade. Conductors entering a building shall be protected by an 
approved enclosure or raceway from the minimum cover 
depth to the point of entrance. Where direct-buried conduc- 
tors, raceways, or cables are subject to movement by settle- 
ment or frost, they shall be installed to prevent damage to the 
enclosed conductors or to the equipment connected to the 
raceways. Metallic enclosures shall be grounded. 

(D) Splices. Direct burial cables shall be permitted to be 
spliced or tapped without the use of splice boxes, provided 
they are installed using materials suitable for the applica- 
tion. The taps and splices shall be watertight and protected 
from mechanical damage. Where cables are shielded, the 
shielding shall be continuous across the splice or tap. 

Exception: At splices of an engineered cabling system, 
metallic shields of direct-buried single-conductor cables 
with maintained spacing between phases shall be permit- 
ted to be interrupted and overlapped. Where shields are 
interrupted and overlapped, each shield section shall be 
grounded at one point. 

(E) Backfill. Backfill containing large rocks, paving mate- 
rials, cinders, large or sharply angular substances, or corro- 
sive materials shall not be placed in an excavation where 
materials can damage or contribute to the corrosion of race- 
ways, cables, or other substructures or where it may pre- 
vent adequate compaction of fill. 

Protection in the form of granular or selected material 
or suitable sleeves shall be provided to prevent physical 
damage to the raceway or cable. 



(F) Raceway Seal. Where a raceway enters from an under- 
ground system, the end within the building shall be sealed 
with an identified compound so as to prevent the entrance 
of moisture or gases, or it shall be so arranged to prevent 
moisture from contacting live parts. 



ARTICLE 310 
Conductors for General Wiring 



I. General 

310.1 Scope. This article covers general requirements for 
conductors and their type designations, insulations, markings, 
mechanical strengths, ampacity ratings, and uses. These re- 
quirements do not apply to conductors that form an integral 
part of equipment, such as motors, motor controllers, and 
similar equipment, or to conductors specifically provided for 
elsewhere in this Code. 

Informational Note: For flexible cords and cables, see Ar- 
ticle 400. For fixture wires, see Article 402. 

310.2 Definitions. 

Electrical Ducts, Electrical conduits, or other raceways 
round in cross section, that are suitable for use underground 
or embedded in concrete. 

Thermal Resistivity. As used in this Code, the heat trans- 
fer capability ihuxnih i Mib t..<n ^ by • •onduaion. It is the 
reciprocal of thermal conductivity and is designated Rho 
and expressed ii the units "C-cm/W. 

II. Installation 

310.10 Uses Permitted. The conductors described in 
310.104 shall be permitted for use in any of the wiring 
methods covered in Chapter 3 and as specified in their 
respective tables or as permitted elsewhere in this Code. 

Informational Note: Thermoplastic insulation may stiffen 
at temperatures lower flsan -10 D C ( + 14°F). Thermoplastic 
insulation ma) also be deformed ai normal temperature; 
where 'i-bje. <i»c3 to pres urs such .. at pt "ii ol suppo t 
I>if rnti>,;U ie insulation, when si ?d on dc circuits in wet 
l(i',iii',n, ma) f .iii p. electroendosmosis between the 
conductor i nd insulation 

(A) Dry Locations. Insulated conductors and cables used in 
dry locations shall be any of the types identified in this Code. 

(B) Dry and Damp Locations. Insulated conductors and 
cables used in dry and damp locations shall be Types FEP, 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-147 



310.10 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, 
THW, THW-2, THHW, THWN, THWN-2, TW, XHH, 
XHHW, XHHW-2, Z, or ZW. 

(C) Wet Locations. Insulated conductors and cables used 
in wet locations shall comply with one of the following: 

(1) Be moisture-impervious metal-sheathed 

(2) Be types MTW, RHW, RHW-2, TW, THW, THW-2, 
THHW, THWN, THWN-2, XHHW, XHHW-2, ZW 

(3) Be of a type listed for use in wet locations 

(D) Locations Exposed to Direct Sunlight. Insulated con- 
ductors or cables used where exposed to direct rays of the 
sun shall comply with (D)(1) or (D)(2): 

(1) Conductors and cables shall be listed, or listed and 
marked, as being sunlight resistant 

(2) Conductors and cables shall be covered with insulating 
material, such as tape or sleeving, that is listed, or 
listed and marked, as being sunlight resistant 

(E) Shielding. Non-shielded, ozone-resistant in ubted con- 
ductor; >> iih .i ui.r ijiiJioplu.' to-phase voltag of 5000 volts 
shall be; permitted in Hype VJC cables in industrial establish- 
ments where ,he conditions ol maintenance arid supervision 
ensure that onl> {]Uil,<u\l persons serviet the installation. For 
other establishments, solid dielectric insulated conductors op- 
erated above 2000 volts in permanent installations shall have 
ozone-resistant insulation and shall be shielded. All metallic 
insulation shields shall be connected to a grounding electrode 
conductor, a grounding busbar, an equipment grounding con- 
ductor, or a grounding electrode. 

Informational Note: The primary purpose; ol hielding arc 
to confine the voltage stresses to the insulation, dissipate 
insulation leakag< mrKi". drain off the eapac tivs tini; ing 
irteni ti»l arrj ground fault mn'i i U 1 > litate < i ra 
tion of ground-fault protective devices in the event of an 
eleiliical cable l.iull 

Exception No. 1: Nonshielded insulated conductors listed 
by a qualified testing laboratory shall be permitted for use 
up to 2400 volts under the following conditions: 

(a) Conductors shall have insulation resistant to elec- 
tric discharge and surface tracking, or the insulated con- 
ductor(s) shall be covered with a material resistant to 
ozone, electric discharge, and surface tracking. 

(b) Where used in wet locations, the insulated conduc- 
tor's) shall have an overall nonmetallic jacket or a continu- 
ous metallic sheath, 

(c) Insulation and jacket thicknesses shall be in accor- 
dance with Table 310.104(D). 

Exception No. 2: No ishield ! ii sal t d < >n liu <m > listed 
In a qualified testing laboratory shall be permitted foi ust 
up to St 00 volts to eplaa exi ting nonshielded <--tf ! ii- 



turs, <<n existing equipment in industrial establishments 
only, unite) the lo^oi ii g conditions: 

(a) Where die condition of maintenance and supervi- 
sion ensurei thai -nl qualified pet onnel install and ser 
vice the installation. 

(b) Conductors shall have insulation resistant to elec- 
tric lisclmrge i"ul surf act tracking, oi the insulated . m 
ductor(s) shall be covered with a material resistant to 
ozone, elect ic dischargt and surf oa tracking. 

(c) Where used in wet locations tin insulated conduc- 
tors ) shall hu\ e cit overall nonnu tallii picket or a c ontinu- 
ous metallic sheath. 

(d) Insulation and jacket thicknesses shall be in accor- 
dance with Table 310.13(D). 

Informational Note: Ri-u.Mion oi replacement of e nip 
ment m '\ nol oomph with the term e i ting as related to 
iliis exception. 

Exception No. 3: Where permitted in 310. 10(F), Exception 
No. 2. 

(F) Direct-Burial Conductors. Conductors used for direct- 
burial applications shall be of a type identified for such use. 

Exception No. 1: Nonshielded multiconductor cables rated 
2001-2400 volts shall be permitted if the cable has an 
overall metallic sheath or armor. 

The metallic shield, sheath, or armor shall be connected 
to a grounding electrode conductor, grounding busbar, or a 
grounding electrode. 

Exception No. 2: Airfield lighting cable used in series cir- 
cuits that are rated up to 5000 volts and are powered by 
regulators shall be permitted to be nonshielded. 

Informational Note to Exception No. 2: Federal Aviation Ad- 
ministration (FAA) Advisory Circulars (ACs) provide addi- 
tional practices and methods for airport lighting. 

Informational Note No. 1: See 300.5 for installation re- 
quirements for conductors rated 600 volts or less. 

Informational Note No. 2: See 300.50 for installation re- 
quirements for conductors rated over 600 volts. 

(G) Corrosive Conditions. Conductors exposed to oils, 
greases, vapors, gases, fumes, liquids, or other sub- 
stances having a deleterious effect on the conductor or 
insulation shall be of a type suitable for the application. 

(H) Conductors in Parallel. 

(1) General. Aluminum copper-clad aluminum, or copper 
conductors kn sach (Utc-. («.>l:nit\. neutral, oi grounded cii 
cult k ',i ill >. permitt xi i>> n. :onn< • ti d in o.uftils-1 (electrically 

I'n'ieJ at both end'-, only in uzes 1/0 \"«b , i,o Lut,-, where 
installed in accordance wnh 510 IOiHi' ') through -H)(6). 



70-148 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



Exception No. 1: Conductors in sizes smaller than 1/0 
AWG shall be permitted to be run in parallel to supply 
control power to indicating instruments, contactors, relays, 
solenoids, and similar control devices, or for frequencies of 
360 Hz and higher, provided all of the following apply: 

(a) They are contained within the same raceway or 
cable. 

(b) The ampacity of each individual conductor is suf- 
ficient to carry the entire load current shared by the paral- 
lel conductors. 

(c) The overcurrent protection is such that the ampac- 
ity of each individual conductor will not be exceeded if one 
or more of the parallel conductors become inadvertently 
disconnected. 

Exception No. 2: Under engineering supervision, 2 AWG 
and 1 AWG grounded neutral to it u toi \ hall he permitted 
to be hi skilled in parallel for existing installations. 

Informational Note to Exception No. 2: Exception No. 2 can 
be used to alleviate overheating of neutral conductors in exist- 
ing installations due to high content of triplen harmonic 
currents. 

(2) Conductor Characteristics. The paralleled conductors 
in each phase, polarity, neutral, grounded circuit ct>u<luve>i 
idii'pir *nt grounding conductor, or equipment bonding 
jumper shall comply with all of the following: 

(1) Be the same length 

(2) Consist of the same conductor material 

(3) Be the same size in circular mil area 

(4) Have the same insulation type 

(5) Be terminated in the same manner 

(3) Separate Cables or Raceways. Where run in separate 
cables or raceways, the cables or raceways with conductors 
shall have the same number of conductors and shall have the 
same electrical characteristics. Conductors of one phase, po- 
larity, neutral, grounded circuit conductor, or equipment 
grounding conductor shall not be required to have the same 
physical characteristics as those of another phase, polarity, 
neutral, grounded circuit conductor, or equipment ground- 
ing conductor. 

(4) Ampacity Adjustment. Conductors installed in paral- 
lel shall comply with the provisions of 310.15(B)(3)(a). 

(5) Equipment Grounding Conductors. Where parallel 
equipment grounding conductors are used, they shall be sized 
in accordance with 250.122. Sectioned equipment grounding 
conductors smaller than 1/0 AWG shall be permitted in mul- 
ticonductor cables in accordance with 310.104, provided the 
combined circular mil area of the sectioned equipment 
(?Miiui<itP£ ioiiJu' tors in each cable complies with 250.122. 



(6) Equipment Bonding Jumpers. Where p rail I equip- 
ment bonding jumpers are installed in raceways, they shall 
be sized and installed in accordance with 250.102. 

310.15 Ampacities for Conductors Rated 0-2000 Volts. 
(A) General. 

(1) Tables or Engineering Supervision. Ampacities for 
conductors shall be permitted to be determined by tables as 
provided in 310.15(B) or under engineering supervision, as 
provided in 310.15(C). 

Informational Note No. 1: Ampacities provided by this 
section do not take voltage drop into consideration. See 
210.19(A), Informational Note No. 4, for branch circuits 
and 215.2(A), Informational Note No. 2, for feeders. 

Informational Note No. 2: For the allowable ampacities of 
Type MTW wire, see Table 13.5.1 in NFPA 79-2007, Elec- 
trical Standard for Industrial Machinery. 

(2) Selection of Ampacity. Where more than one ampacity 
applies for a given circuit length, the lowest value shall be 
used. 

Exception: Where two different ampacities apply to adjacent 
portions of a circuit, the higher ampacity shall be permitted to 
be used beyond tlie point of transition, a distance equal to 3.0 
m (10 ft) or 10 percent of the circuit length figured at the 
higher ampacity, whichever is less. 

Informational Note: See 1 10.14(C) for conductor tempera- 
ture limitations due to termination provisions. 

(3) Temperature Limitation of Conductors. No conduc- 
tor shall be used in such a manner that its operating tem- 
perature exceeds that designated for the type of insulated 
conductor involved. In no case shall conductors be associ- 
ated together in such a way, with respect to type of circuit, 
the wiring method employed, or the number of conductors, 
that the limiting temperature of any conductor is exceeded. 

Informational Note No. 1: The temperature rating of a 
conductor [see Table 310.104(A) and Table 310.104(C)] is 
the maximum temperature, at any location along its length, 
that the conductor can withstand over a prolonged time 
period without serious degradation. The allowable ampacity 
tables, the ampacity tables of Article 310 and the ampacity 
tables of Informative Annex B. the ambient temperature 
correction factors in 3 10. 15(B)(2). and the notes to the 
tables provide guidance for coordinating conductor sizes, 
types, allowable ampacities, ampacities, ambient tempera- 
tures, and number of associated conductors. The principal 
determinants of operating temperature are as follows: 

(1) Ambient temperature — ambient temperature may vary 
along the conductor length as well as from time to 
time. 

(2) Heat generated internally in the conductor as the result 
of load current flow, including fundamental and har- 
monic currents. 



2011 Edition 



NATIONAL BLECTR1CAL CODE 



70-149 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



(3) The rate at which generated heat dissipates into the 
ambient medium. Thermal insulation that covers or sur- 
rounds conductors affects the rate of heat dissipation. 

(4) Adjacent load-carrying conductors — adjacent conduc- 
tors have the dual effect of raising the ambient tempera- 
ture and impeding heat dissipation. 

Informational Note No. 2 : Refer to 1 1 0. 1 4( C ) foi I he tem- 
perature limitation <>f tefmlnations. 

(B) Tables. Ampacities for conductors rated to 2000 volts 
shall be as specified in the Allowable Ampacity Table 
310.15(B)(16) through Table 3I().I5(B)(19). and Ampacity 
Tabic 310.15<B)(20) and Table 310.15(B)(2) ) as modified by 
310.15(B)(1) through (B)(7). 

The temperature correction and adjustment factors shall 
be permitted to be applied to the' ampacitj foi the tempera- 
ture rating o( the conductoi i1 the correcte I nd adjusted 
i mpacity doe 1 , nm e :ceed the ampacity )",»■ the temperature 
rating of the termination in accordance with the provisions 
of 11 0.1 4(C). 

Informational Note: Table 310.15(B)(16) through Table 
3l0.15(Bid9) are application tables for use in determining 
conductor sizes on loads calculated in accordance with Ar- 
ticle 220. Allowable ampacities result from consideration of 
one or more of the following: 

(1) Temperature compatibility with connected equipment, 
especially the connection points. 

(2) Coordination with circuit and system overcurrent pro- 
tection. 

(3) Compliance with the requirements of product listings 
or certifications. See 110.3(B). 

(4) Preservation of the safety benefits of established indus- 
try practices and standardized procedures. 

(1) General. For explanation of type letters used in tables 
and for recognized sizes of conductors for the various conduc- 
tor insulations, see Table 310.104(A) and Table 310.104(B). 
For installation requirements, see 310.1 through 310.15(A)(3) 
and the various articles of this Code. For flexible cords, see 
Table 400.4, Table 400.5(A)(1), and Table 400.5(A)(2). 

(2) Ambient Temperature Correction Factors. Ampaci- 

iic ioi ambient temperatures othei ij.-itj those -!w n m the 
ampacity tables shall be corrected in tccordance wish Table 
310.15(B)(2)(a) or Table 3 10,1 5(B)(2)(b), or shall be per- 
mitted to be calculated using the iollov ins equation: 



/' = / 



- T 



T-T 



where: 
/' = ampacity corrected lor ambient temperature 
/ = ampacity shown in the tables 
T e = temperature rating of conductor (°Q 
T u ' = new ambient temperature (°C) 
T a = ambient temperature used in the table (°C) 



Table 310.15(B)(2)(a) Ambient Temperature Correction 
Factors Based on 30°C (86°F) 

For ambient temperatures other than 30°C (86°F), multiply the 

allowable ampacities specified in the ampacity tables by the 

appropriate correction factor shown below. 



Ambient 


Temperature Rating of Conductor 


Ambient 


Temperature 

(°C) 


60°C 


75°C 


90°C 


Temperature 

(°F) 


1 or less 


1.29 


1.20 


1.15 


50 or less 


11-15 


1.22 


1.15 


1.12 


51-59 


16-20 


1.15 


1.11 


1.08 


60-68 


21-25 


1.08 


1.05 


1.04 


69-77 


26-30 


1.00 


1.00 


1.00 


78-86 


31-35 


0.91 


0.94 


0.96 


87-95 


36-40 


0.82 


0.88 


0.91 


96-104 


41-45 


0.71 


0.82 


0.87 


105-113 


46-50 


0.58 


0.75 


0.82 


114-122 


51-55 


0.41 


0.67 


0.76 


123-131 


56-60 


— 


0.58 


0.71 


132-140 


61-65 


— 


0.47 


0.65 


141-149 


66-70 


— 


0.33 


0.58 


150-158 


71-75 


— 


— 


0.50 


159-167 


76-80 


— 


— 


0.41 


168-176 


81-85 


— 


— 


0.29 


177-185 



(3) Adjustment Factors. 

(a) More Than Three Current-Carrying Conductors in a 
Raceway or Cable. Where the number of current-carrying 
conductors in a raceway or cable exceeds three, or where 
single conductors or multiconductor cables are installed 
without maintaining spacing for a continuous length longer 
than 600 mm (24 in.) and are not installed in raceways, the 
allowable ampacity of each conductor shall be reduced as 
shown in Table 310.15(B)(3)(a). Each current-carrying con- 
ductor of a paralleled set of conductors shall be counted as 
a current-carrying conductor. 

Where conductors of different systems, as provided in 
300.3, are installed in a common raceway or cable, the 
adjustment factors shown in Table 310.15(B)(3)(a) shall 
apply only to the number of power and lighting conductors 
(Articles 210, 215, 220, and 230). 

Informational Note No. 1: See Annex B, Table 
B. 310. 15(B)(2)(H), for adjustment factors for more than 
three current-carrying conductors in a raceway or cable 
with load diversity. 



70-150 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



Table 310.15(B)(2)(b) Ambient Temperature Correction Factors Based on 40°C (104°F) 



For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities specified in the ampacity tables by the appropriate 

correction factor shown below. 



Ambient 


Temperature Rating of Conductor 


Ambient 


Temperature 

(°C) 


60°C 


75°C 


90°C 


150°C 


200°C 


250°C 


Temperature 

(°F) 


10 or less 


1.58 


1.36 


1.26 


1.13 


1.09 


1.07 


50 or less 


11-15 


1 .50 


1.31 


1.22 


1.11 


1.08 


1.06 


51-59 


16-20 


1.41 


1.25 


1.18 


1.09 


1.06 


1.05 


60-68 


21-25 


1.32 


1.2 


1.14 


1.07 


1.05 


1.04 


69-77 


26-30 


1.22 


1.13 


1.10 


1.04 


1.03 


1.02 


78-86 


31-35 


1.12 


1.07 


1.05 


1.02 


1.02 


1.01 


87-95 


36^*0 


1.00 


1.00 


1.00 


1.00 


1.00 


1.00 


96-104 


41-45 


0.87 


0.93 


0.95 


0.98 


0.98 


0.99 


105-113 


46-50 


0.71 


0.85 


0.89 


0.95 


0.97 


0.98 


114-122 


51-55 


0.50 


0.76 


0.84 


0.93 


0.95 


0.96 


123-131 


56-60 


— 


0.65 


0.77 


0.90 


0.94 


0.95 


132-140 


61-65 


— 


0.53 


0.71 


0.88 


0.92 


0.94 


141-149 


66-70 


— 


0.38 


0.63 


0.85 


0.90 


0.93 


150-158 


71-75 


— 


' — 


0.55 


0.83 


0.88 


0.91 


159-167 


76-80 


— 


— 


0.45 


0.80 


0.87 


0.90 


168-176 


81-90 


— 


— 


— 


0.74 


0.83 


0.87 


177-194 


91-100 


— 


— 


— 


0.67 


0.79 


0.85 


195-212 


101-110 


— 


— 


— 


0.60 


0.75 


0.82 


213-230 


111-120 


— 


— 


— 


0.52 


0.71 


0.79 


23 1-248 


121-130 


— 


— 


— 


0.43 


0.66 


0.76 


249-266 


131-140 


— 


— 


— 


0.30 


0.61 


0.72 


267-284 


141-160 


— 


— 


— 


— 


0.50 


0.65 


285-320 


161-180 


— 


— 


— 


— 


0.35 


0.58 


321-356 


181-200 


— 


— 


— 


— 


— 


0.49 


357-392 


201-225 


— 


— 


~ 


— 


— 


0.35 


393^137 



20 1 1 Edition NATIONAL ELECTRICAL CODE 



70-151 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.15(B)(3)(a) Adjustment Factors for More Than 
Three Current-Carrying Conductors in a Raceway or Cable 





Percent of Values in 




Tabic 3H).I5(B)(16) through 




Table 310.15(101 19) as 


Number of 


Adjusted for Ambient 


Conductors 1 


Temperature if Necessary 


4-6 


80 


7-9 


70 


1.0-20 


50 


21.-30 


45 


31^0 


40 


41 and above 


35 



'Number of conductors is the total number of condus tors in the race- 
waj or cable adjusted in ao irdunce with 310.15(B)(5) md (6). 

Informational Note No. 2: See 366.23(A) for adjustment 
factors for conductors in sheet metal auxiliary gutters and 
376.22(B) for adjustment factors for conductors in metal 
wireways. 

(1) Where conductors are installed in cable trays, the 
provisions of 392.80 shall apply. 

(2) Adjustment factors shall not apply to conductors 
in raceways having a length not exceeding 
600 mm (24 in.). 

(3) Adjustment factors shall not apply to underground 
conductors entering or leaving an outdoor trench if those 
conductors have physical protection in the form of rigid 
metal conduit, intermediate metal conduit, rigid polyvinyl 
chloride conduit (PVC), or reinforced thermosetting rfesiii 
conduit (RTRC) having a length not exceeding 3.05 m 
(10 ft); and if the number of conductors does not exceed 
four. 

(4) Adjustment factors shall not apply to Type AC 
cable or to Type MC cable under the following conditions: 

a. The cables do not have an overall outer jacket. 

b. Each cable has not more than three current-carrying 
conductors. 

c. The conductors are 12 AWG copper. 

d. Not more than 20 current-carrying conductors are in- 
stalled without maintaining spacing, are stacked, or are 
supported on"bridle rings." 

(5) An adjustment factor of 60 percent shall be applied 
to Type AC cable or Type MC cable under the following 
conditions: 

a. The cables do not have an overall outer jacket. 

b. The number of current carrying conductors « xceetis 20, 

c. The cables are stacked or bundled longei thai 600 mm 
(24 in) without spacing being maintained. 

(b) More Than One Conduit, Tube, or Raceway. Spacing 
between conduits, tubing, or raceways shall be maintained. 

(c) Circular Raceways Exposed to Sunlight on Roof- 
tops. Where conductors or cables are installed in circtil t: 



raceways exposed to direct sunlight on or above rooftops, 
the adjustments shown in Table 310.15(B)(3)(c) shall be 
added to the outdoor temperature to determine the appli- 
cable ambient temperature for application of the correction 

factors in Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b). 

Informational Note: One source for the average ambient 
temperatures in various locations is the ASHRAE Hand- 
book — Fundamentals. 



Table 310.15(B)(3)(c) Ambient Temperature Adjustment for 
Circular Raceways Exposed to Sunlight on or Above 
Rooftops 



Temperature Adder 



Conduit 


°C 


°F 


0-13 mm i. 1 /- in.) 


33 


60 


Above 13 mm ( [ A in.)-90 mm (3!/2 in.) 


22 


40 


Above 90 mm (3!/i in.)-300 mm 


17 


30 


(12 in.) 






Above 300 mm (12 in.)-900 mm 


14 


25 


(36 in.) 







Informational Note to Table 310.15(B)(3)(c): The temperature 
adders in Table 310.15(B)(3)(c) are based on the results of 
averaging the ambient temperatures. 

(#) Bare or Covered Conductors. Where bare or covered 
conductors are installed with insulated conductors, the tem- 
perature rating of the bare or covered conductor shall be 
equal to the lowest temperature rating of the insulated con- 
ductors for the purpose of determining ampacity. 

(5) Neutral Conductor. 

(a) A neutral conductor that carries only the unbalanced 
current from other conductors of the same circuit shall not be 
required to be counted when applying the provisions of 
310.15(B)(3)(a). 

(b) In a 3-wire circuit consisting of two phase conductors 
and the neutral conductor of a 4-wire, 3-phase, wye-connected 
system, a common conductor carries approximately the same 
current as the line-to-neutral load currents of the other conduc- 
tors and shall be counted when applying the provisions of 
310.15(B)(3)(a). 

(c) On a 4-wire, 3-phase wye circuit where the major 
portion of the load consists of nonlinear loads, harmonic cur- 
rents are present in the neutral conductor; the neutral conduc- 
tor shall therefore be considered a current-carrying conductor. 

(6) Grounding or Bonding Conductor. A grounding or 
bonding conductor shall not be counted when applying the 
provisions of 310.15(B)(3)(a). 



70-152 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



(7) 120/240-Volt, 3-Wire, Single-Phase Dwelling Ser- 
vices and Feeders. For individual dwelling units of one- 
family, two-family, and multifamily dwellings, conductors, 
as listed in Table 310.15(B)(7), shall be permitted as 
1 20/240-volt, 3-wire, single-phase service-entrance con- 
ductors, service-lateral conductors, and feeder conductors 
that serve as the main power feeder to each dwelling unit 
and are installed in raceway or cable with or without an 
equipment grounding conductor. For application of this sec- 
tion, the main power feeder shall be the feeder between the 
main disconnect and the panelboard that supplies, either by 
branch circuits or by feeders, or both, all loads that are part 
or associated with the dwelling unit. The feeder conductors 
to a dwelling unit shall not be required to have an allowable 
ampacity rating greater than their service-entrance conduc- 
tors. The grounded conductor shall be permitted to be 
smaller than the ungrounded conductors, provided the re- 
quirements of 215.2, 220.61, and 230.42 are met. 

(C) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by means of the following general equation: 



/ = 



T-r 



Table 310.15(B)(7) Conductor Types and Sizes for 
120/240-Volt, 3- Wire, Single-Phase Dwelling Services and 
Feeders. Conductor Types RHH, RHW, RHW-2, THHN, 
THHW, THW, THW-2, THWN, THWN-2, XHH W, 

XHHW-2, SE, USE, USE-2 



Conductor (AWG or kcmil) 






Aluminum or 


Service or Feeder 




Copper-Clad 


Rating (Amperes) 


Copper 


Aluminum 


100 


4 


2 


110 


3 


1 


125 


2 


1/0 


150 


1 


2/0 


175 


1/0 


3/0 


200 


2/0 


4/0 


225 


3/0 


250 


250 


4/0 


300 


300 


250 


350 


350 


350 


500 


400 


400 


600 



**(i+W 



- xlO' 1 amperes 



T„ 



where: 

T- c = conductor temperature in degrees Celsius (°C) 
= ambient temperature in degrees Celsius (°C) 
= dc resistance of conductor at temperature T c 
- component ac resistance resulting from skin 

effect and proximity effect 
= effective thermal resistance between conductor 
and surrounding ambient 



R 



R 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-153 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.15(B)(16) (formerly Table 310.16) Allowable Ampacities of Insulated Conductors Rated lip to and Including 2000 
Volts, 60°C Through 90°C (140°F Through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or 
Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F)f 





Temperature Rating of Conductor [See Table 310.104(A).] 












60°C 










60°C (140°F) 


75°C (167°F) 


90°C (194°F) 


(140°F) 


75°C (167°F) 


90°C (194°F) 










Types TBS, SA, 
















SIS, FEP, 
















FEPB, MI, 
















RHH, RHW-2, 






Types TBS, SA, 










THHN, THHW, 






SIS, THHN, 










THW-2, 






THHW, THW-2, 








Types RHW, 


THWN-2, 




Types RHW, 


THWN-2, RHH, 








THHW, THW, 


USE-2, XHH, 




THHW, THW, 


RHW-2, USE-2, 




Size AWG or 




THWN, XHHW, 


XHHW, 


Types TW, 


THWN, XHHW, 


XHH, XHHW, 




kcmil 


Types TW, UF 


USE, ZW 


XHHW-2, ZW-2 


UF 


USE 


XHHW-2, ZW-2 












ALUMINUM OR COPPER-CLAD 








COPPER 




ALUMINUM 


Size AWG or kcmil 


18 






14 




_ 








16 


— 


— 


18 


— 


— 


— 


— 


148* 


15 


20 


25 


— 


— 


— 


— 


1 2** 


20 


25 


30 


15 


20 


25 


12** 


10** 


30 


35 


40 


25 


30 


35 


10** 


8 


40 


50 


55 


35 


40 


45 


8 


6 


55 


65 


75 


40 


50 


55 


6 


4 


70 


85 


95 


55 


65 


75 


4 


3 


85 


100 


115 


65 


75 


85 


3 


2 


95 


115 


130 


75 


90 


100 


2 


1 


110 


130 


145 


85 


100 


115 


1 


1/0 


125 


150 


170 


100 


120 


135 


1/0 


2/0 


145 


175 


195 


115 


135 


150 


2/0 


3/0 


165 


200 


225 


130 


155 


175 


3/0 


4/0 


195 


230 


260 


150 


180 


205 


4/0 


250 


215 


255 


290 


170 


205 


230 


250 


300 


240 


285 


320 


195 


230 


260 


300 


350 


260 


310 


350 


210 


250 


280 


350 


400 


280 


335 


380 


225 


270 


305 


400 


500 


320 


380 


430 


260 


310 


350 


500 


600 


350 


420 


475 


285 


340 


385 


600 


700 


385 


460 


520 


315 


375 


425 


700 


750 


400 


475 


535 


320 


385 


435 


750 


800 


410 


490 


555 


330 


395 


445 


800 


900 


435 


520 


585 


355 


425 


480 


900 


1000 


455 


545 


615 


375 


445 


500 


1000 


1250 


495 


590 


665 


405 


485 


545 


1250 


1500 


525 


625 


705 


435 


520 


585 


1500 


1750 


545 


650 


735 


455 


545 


615 


1750 


2000 


555 


665 


750 


470 


560 


630 


2000 



Refer to 310 I5(B)<2> for the ampacity correction factor*, when hi ambien temperature i: othct than 50°0 (86 C 'F) 
' Relet t > 240.4(D) J u eonduetot overcurrenl protection [imitations 



70^154 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.15 



Table 310.15<li)< 17) (formerly Table 310.17) Allowable Ampacities of Single-Insulated Conductors Rated L ! p to and Including 
2000 Volts in Free Air, Based on Ambient Temperature of 30°C (86°F)* 





Temperature Rating of Conductor [See Table 310.104(A).] 






60°C (140°F) 


75°C (167°F) 


90°C (194°F) 


60°C (140°F) 


75°C (167°F) 


90°C (194°F) 










Types TBS, SA, SIS, 






Types TBS, SA, SIS, 










FEP, FEPB, MI, RHH, 






THHN, THHW, 








Types RHW, 


RHW-2, THHN, THHW, 




Types RHW, 


THW-2, THWN-2, 








THHW, THW, 


THW-2, THWN-2, 




THHW, THW, 


RHH, RHW-2, USE-2, 








THWN, 


USE-2, XHH, XHHW, 




THWN, 


XHH, XHHW, 




Size AWG or 


Types TW, UF 


XHHW, ZW 


XHHW-2, ZW-2 


Types TW, UF 


XHHW 


XHHW-2, ZW-2 
















Size AWG or 


kcmil 




COPPER 


ALUMINUM OR COPPER-CLAD ALUMINUM 


kcmil 


18 


_ 




18 










16 


— 


— 


24 












14** 


25 


30 


35 












1 2** 


30 


35 


40 


25 


30 


35 


1 2** 


10** 


40 


50 


55 


35 


40 


45 


10** 


8 


60 


70 


80 


45 


55 


60 


8 


6 


80 


95 


105 


60 


75 


85 


6 


4 


105 


125 


140 


80 


100 


115 


4 


3 


120 


145 


165 


95 


115 


130 


3 


2 


140 


170 


190 


110 


135 


150 


2 


1 


165 


195 


220 


130 


155 


175 


1 


1/0 


195 


230 


260 


150 


180 


205 


1/0 


2/0 


225 


265 


300 


175 


210 


235 


2/0 


3/0 


260 


310 


350 


200 


240 


270 


3/0 


4/0 


300 


360 


405 


235 


280 


315 


4/0 


250 


340 


405 


455 


265 


315 


355 


250 


300 


375 


445 


500 


290 


350 


395 


300 


350 


420 


505 


570 


330 


395 


445 


350 


400 


455 


545 


615 


355 


425 


480 


400 


500 


515 


620 


700 


405 


485 


545 


500 


600 


575 


690 


780 


455 


545 


615 


600 


700 


630 


755 


850 


500 


595 


670 


700 


750 


655 


785 


885 


515 


620 


700 


750 


800 


680 


815 


920 


535 


645 


725 


800 


900 


730 


870 


980 


580 


700 


790 


900 


1000 


780 


935 


1055 


625 


750 


845 


1000 


1250 


890 


1065 


1200 


710 


855 


965 


1250 


1500 


980 


1175 


1325 


795 


950 


1070 


1500 


1750 


1070 


1280 


1445 


875 


1050 


1185 


1750 


2000 


1155 


1385 


1560 


960 


1150 


1295 


2000 



Refei to 310.15(B)(2) tor the ampacity correction i ictors where ih ambient itmp. rature is other than 30°C (86' F). 
1 Refer to 240 4(D) for conductoi own urrenl protei tion limitations. 



2011 Edition NATIONAL ELECTRICAL CODE 



70-155 



310.15 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.15(H)! IS! (formerly Table 310.18) Allowable Ampacities of Insulated Conductors Rated l'p to and including 2000 
Volts, 150°C Through 250°C (302°F Through 482°F). Not More Than Three Current-Carrying Conductors in Raceway or 
Cable, Based on Ambient Air Temperature of 40°C (104°F)* 



— 


Temperature Rating of Conductor [See Table 310.104(A).] 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 






TypeZ 


Types FEP, FEPB, 
PFA, SA 


Types PFAH, TFE 


TypeZ 




Size AWG or kcmil 


COPPER 


NICKEL OR 

NICKEL-COATED 

COPPER 


ALUMINUM OR 

COPPER-CLAD 

ALUMINUM 


Size AWG or kcmil 


14 

12 

10 

8 


34 

43 
55 
76 


36 
45 
60 

83 


39 

54 
73 
93 


30 

44 
57 


14 

12 

10 

8 


6 

4 
3 

2 


96 
120 
143 
160 
186 


110 
125 
152 
171 
197 


117 
148 
166 
191 
215 


75 

94 

109 

124 
145 


6 

4 
3 

2 


1/0 

2/0 
3/0 

4/0 


215 
251 
288 
332 


229 
260 
297 
346 


244 
273 
308 
361 


169 
198 

227 
260 


1/0 

2/0 
3/0 
4/0 



*Refer to 310.15(B)(2) for the ampacity correction factors where the ambient temperature is other than 40'C (.104 h). 



Table 310.15(B)(19) (formerly Table 310.19) Allowable Ampacities of Single-Insulated Conductors, Rated l'p to and Including 
2000 Volts, 150°C Through 250°C (302°F Through 482°F), in Free Air, Based on Ambient Air Temperature of 40°C (104°F)* 





Temperature Rating of Conductor [See Table 310.104(A).] 






150°C (302°F) 


200°C (392°F) 


250°C (482°F) 


150°C (302°F) 






TypeZ 


Types FEP, 
FEPB, PFA, SA 


Types PFAH, TFE 


TypeZ 




Size AWG or kcmil 


COPPER 


NICKEL, OR 
NICKEL-COATED COPPER 


ALUMINUM OR 

COPPER-CLAD 

ALUMINUM 


Size AWG or kcmil 


14 

12 

10 

8 


46 

60 

80 

106 


54 
68 
90 
124 


59 

78 

107 

142 


47 
63 
83 


14 

12 

10 

8 


6 

4 
3 
2 
1 


155 
190 
214 
255 
293 


165 
220 

252 
293 

344 


205 
278 
327 
381 
440 


112 
148 
170 
198 

228 


6 

4 
3 
2 
1 


1/0 

2/0 
3/0 
4/0 


339 
390 
451 

529 


399 
467 
546 
629 


532 
591 
708 
830 


263 
305 

351 
411 


1/0 
2/0 
3/0 
4/0 



■'Refer to 310. 15(B)(2) for the ampacity correction factors where the ambient temperature is other than 40 C C I KMT). 



70-156 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.15<B)<20) (formerly Table 310.20) Ampacities of Not More Than Three Single Insulated Conductors, Rated Up to and 
Including 20<HI Volts, Supported on a Messenger, Based on Ambient Air Temperature of 40°C (104°F)* 





Temperature Rating of Conductor [See Table 310.104(A).] 






75°C (167°F) 


90°C (194°F) 


75°C (167°F) 


90°C (194°F) 








Types MI, THHN, 












THHW, THW-2, 




Types THHN, THHW, 






Types RHW, THHW, 


THWN-2, RHH, RHW-2, 




RHH, XHHW, RHW-2, 






THW, THWN, 


USE-2, XHHW, 


Types RHW, THW, 


XHHW-2, THW-2, 






XHHW, ZW 


XHHW-2, ZW-2 


THWN, THHW, XHHW 


THWN-2, USE-2, ZW-2 




Size AWG or kcmil 


COPPER 


ALUMINUM OR COPPER-CLAD ALUMINUM 


Size AWG or kcmil 


8 


57 


66 


44 


51 


8 


6 


76 


89 


59 


69 


6 


4 


101 


117 


78 


91 


4 


3 


118 


138 


92 


107 


3 


2 


135 


158 


106 


123 


2 


1 


158 


185 


123 


144 


1 


1/0 


183 


214 


143 


167 


1/0 


2/0 


212 


247 


165 


193 


2/0 


3/0 


245 


287 


192 


224 


3/0 


4/0 


287 


335 


224 


262 


4/0 


250 


320 


374 


251 


292 


250 


300 


359 


419 


282 


328 


300 


350 


397 


464 


312 


364 


350 


400 


430 


503 


339 


395 


400 


500 


496 


580 


392 


458 


500 


600 


553 


647 


440 


514 


600 


700 


610 


714 


488 


570 


700 


750 


638 


747 


512 


598 


750 


800 


660 


773 


532 


622 


800 


900 


704 


826 


572 


669 


900 


1000 


748 


879 


612 


716 


1000 



Porei to 310.15(B)! .') in, (he jirpaui, correction factors where the ambient temperature is othei than 40 l (KM r-i 



Table 310.15(B)(2)) (formerly Table 310.21) Ampacities of Bare or Covered Conductors in Free Air, Based on 40 C (104 F) 
Ambient, 80°C (176°F) Total Conductor Temperature, 610 mm/sec (2 ft/sec) Wind Velocity 





Copper Conductors 






AAC Aluminum Conductors 






Bare 




Covered 




Bare 




Covered 


AWG or 




AWG or 




AWG or 




AWG or 




kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


kcmil 


Amperes 


8 


98 


8 


103 


8 


76 


8 


80 


6 


124 


6 


130 


6 


96 


6 


101 


4 


155 


4 


163 


4 


121 


4 


127 


2 


209 


2 


219 


2 


163 


2 


171 


1/0 


282 


1/0 


297 


1/0 


220 


1/0 


231 


2/0 


329 


2/0 


344 


2/0 


255 


2/0 


268 


3/0 


382 


3/0 


401 


3/0 


297 


3/0 


312 


4/0 


444 


4/0 


466 


4/0 


346 


4/0 


364 


250 


494 


250 


519 


266.8 


403 


266.8 


423 


300 


556 


300 


584 


336.4 


468 


336.4 


492 


500 


773 


500 


812 


397.5 


522 


397.5 


548 


750 


1000 


750 


1050 


477.0 


588 


477.0 


617 


1000 


1193 


1000 


1253 


556.5 


650 


556.5 


682 





__ 








636.0 


709 


636.0 


744 








— 


— 


795.0 


819 


795.0 


860 








— 





954.0 


920 


— 


— 











— 


1033.5 


968 


1033.5 


1017 








— 


— 


1272 


1103 


1272 


1201 














1590 


1267 


1590 


1381 


— 


— 


— 


— 


2000 


1454 


2000 


1527 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-157 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 Conductors Rated 2001 to 35,000 Volts. 

(A) Definitions. 

Electrical Ducts. As used in Article 310, electrical ducts 
shall include any of the electrical conduits recognized in 
Chapter 3 as suitable for use underground; other raceways 
round in cross section, listed for underground use, and em- 
bedded in earth or concrete. 

Thermal Resistivity. As used in this Code, the heat trans- 
fer capability through a substance by conduction. It is the 
reciprocal of thermal conductivity and is designated Rho 
and expressed in the units °C-cm/watt. 

(B) Ampacities of Conductors Rated 2001 to 35,000 Volts. 

Ampacities for solid dielectric-insulated conductors shall 
be permitted to be determined by tables or under engineer- 
ing supervision, as provided in 310.60(C) and (D). 

(1) Selection of Ampacity. Where more than one calcu- 
lated or tabulated ampacity could apply for a given circuit 
length, the lowest value shall be used. 

Exception: Where two different ampacities apply to adja- 
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis- 
tance equal to 3.0 in (10 ft) or 10 percent of the circuit 
length calculated at the higher ampacity, whichever is less. 

Informational Note: See 110.40 for conductor temperature 
limitations due to termination provisions. 

(C) Tables. Ampacities for conductors rated 2001 to 35,000 
volts shall be as specified in Table 310 60(0(67) through 
Table 310 6. •> '■, ' i) Ampacities for ambient temperatures 
other than those specified in the ampacity tables shall be cor- 
rected in accordance with 310.60(C)(4). 

Informational Note No. 1: For ampacities calculated in 
accordance with 310.60(B), reference IEEE 835-1994 (IP- 
CEA Pub. No. P-46-426), Standard Power Cable Ampacity 
Tables, and the references therein for availability of all fac- 
tors and constants. 

Informational Note No. 2: Ampacities provided by this 
section do not take voltage drop into consideration. See 
210.19(A), Informational Note No. 4, for branch circuits 
and 215.2(A), Informational Note No. 2, for feeders. 

(1) Grounded Shields. Ampacities shown in Table 
310.60(0(69). Table 310.60(0(70), Table 310.60(0(81), and 
Table 310.60(0(82) are for cable with shields grounded at 
one point only. Where shields are grounded at more than one 
point, ampacities shall be adjusted to take into consideration 
the heating due to shield currents. 

(2) Burial Depth of Underground Circuits. Where the 
burial depth of direct burial or electrical duct bank circuits is 
modified from the values shown in a figure or table, ampaci- 



ties shall be permitted to be modified as indicated in (C)(2)(a) 
and (C)(2)(b). 

(a) Where burial depths are increased in part(s) of an 
electrical duct run, no decrease in ampacity of the conduc- 
tors is needed, provided the total length of parts of the duct 
run increased in depth is less than 25 percent of the total 
run length. 

(b) Where burial depths are deeper than shown in a 
specific underground ampacity table or figure, an ampacity 
derating factor of 6 percent per 300-mm (1-ft) increase in 
depth for all values of rho shall be permitted. 

No rating change is needed where the burial depth is 
decreased. 

(3) Electrical Ducts in Figure 310.60. At locations where 
electrical ducts enter equipment enclosures from under 
ground, spacing between such ducts, as shown in Figure 
310.60, shall be permitted to be reduced without requiring 
the ampacity of conductors therein to be reduced. 

(4) Ambient Temperature * 'orrection. Ampacities for 
ambient temperatures other than those specified in the am- 
pacity tables shall be corrected in accordance with Tabic 
310.6Q(C)(4)(4) or shall be permitted to be calculated using 
.he following •.•filiation: 



r=i 



T r -T„ 
T-T 



where: 

/' = ampacity cmeuc ! foi ambient It mi» r.iiim- 
/ = ampacity shown in the table Soi T L and T a 

T L - temperature rating of Conductoi (°C) 
T n ' = new .i >i>>ici.t temperature (°C) 

T a = astir,., -'if ten iperature used i<> the •.■i\M ( O 

(D) Engineering Supervision. Under engineering supervi- 
sion, conductor ampacities shall be permitted to be calcu- 
lated by using the following general equation: 



T,-(T a +M]) 
R.M + YM:. 



X 10" amperes 



where: 
T = conductor temperature i O 
l[, = ambient temperature (C) 

AT d - dielectric loss temperature rise 
R c/l = d< resistance of « onductoi a! tei iperature T 
Y t = component ac resistant c resulting from skin 

cfK-ci and proximity effect 
K„ - t 'lf- J, -ii , e thermal resistance between cotidiKici 

and surrounding ambient 

Informational Note: The dielectric loss temperature rise 
(AT d ) 'a negligible foi single circuit extruded dielectric 
cab! t rated below a 6 kV. 



70-158 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 





^ c B ', 
















w ( aat 


. 






."(i/. 








N 








¥ v^~ 


F 




Detail 1 




M T- T-" 


o 




290 mm x 290 mm 




U J 






(11.5 in.x 11.5 in.) 


190 mm (7.5 in.) 




Electrical duct bank 


Detail 2 




One electrical duct 


475 mm x 475 mm 
(19 in. x 19 in.) 
Electrical duct bank 
Three electrical ducts 
or 






•* G)' & & 






y^ ^W > ^s ^ 






190 mm 190 mm 






(7.5 in.) (7.5 in.) 


LO 




675 mm x 290 mm 


E 
E 




(27 in.x 11 .5 in.) 




Electrical duct bank 


o 








Three electrical ducts 


*- 




190 mm (7.5 in.) 

Detail 3 

475 mm x 675 mm 
(19 in.x 27 in.) 
Electrical duct bank 
Six electrical ducts 




190 mm 
(7.5 in.) 



190 mm 
(7.5 in.) 



675 mm x 475 mm 
(27 in.x 19 in.) 
Electrical duct bank 
Six electrical ducts 



r 



600 mm 



Detail 5 

Buried 3 

conductor 

cable 



(24 in.) 



Detail 6 

Buried 3 

conductor 

cables 



1 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 

rn 



Detail 9 

Buried single-conductor 
cables (1 circuit) 



Detail 7 

Buried triplexed 
cables (1 circuit) 



190 mm 190 mm 
(7.5 in.) (7.5 in.) 



.c 



600 mm 



(24 in.) 



I 



600 mm 



Detail 8 

Buried triplexed 
cables (2 circuits) 

190 mm 190 mm 
(7.5 in.) (7.5 in.) 



(24 in.) 



Detail 10 

Buried single-conductor 
cables (2 circuits) 



Note: Minimum burial depths to top electrical ducts or cables shall be 
in accordance with 300.50. Maximum depth to the top of electrical 
duct banks shall be 750 mm (30 in.) and maximum depth to the top 
of direct buried cables shall be 900 mm (36 in.). 



Legend 

l'°''°l Backfill (earth or concrete) 
W Electrical duct 
• Cable or cables 



Figure 310.60 Cable Installation Dimensions for Use with Table 310.60(0(77) Through Table 
310.60(0(86). 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-159 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.60(C)(4) Ambient Temperature Correction Factors 

For ambient temperatures other than 40°°C (104°F), multiply the 

allowable ampacities specified in the ampacity tables by the 

appropriate factor shown below. 



Ambient 


Temperature Rating of Conductor 


Ambient 


Temperature 

PC) 


90°C 


105°C 


Temperature 

(°F) 


10 or less 


1.26 


1.21 


50 or less 


11-15 


1.22 


1.18 


51-59 


16-20 


1.18 


1.14 


60-68 


21-25 


1.14 


1.11 


69-77 


26-30 


1.10 


1.07 


78-86 


31-35 


1.05 


1.04 


87-95 


36-40 


1.00 


1.00 


96-104 


41^15 


0.95 


0.96 


105-113 


46-50 


0.89 


0.92 


114-122 


51-55 


0.84 


0.88 


123-131 


56-60 


0.77 


0.83 


132-140 


61-65 


0.71 


0.78 


141-149 


66-70 


0.63 


0.73 


150-158 


71-75 


0.55 


0.68 


159-167 


76-80 


0.45 


0.62 


168-176 


81-85 


0.32 


0.55 


177-185 


86-90 


— 


0.48 


186-194 


91-95 


— 


0.39 


195-203 


96-100 


— 


0.28 


204-212 



Table 310.60(0(68) Ampacities of Insulated Single 
Aluminum Conductor Cables Triplexed in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221 °F) 
and Ambient Air Temperature of 40°C (104°F)* 

Temperature Rating of Conductor 
[See Table 310.104(C).] 





2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 




10S°C 




105°C 


Size 


90°C 


(221°F) 


90°C 


(221°F) 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


50 


57 






6 


70 


77 


75 


84 


4 


90 


100 


100 


110 


2 


125 


135 


130 


150 


1 


145 


160 


150 


175 


1/0 


170 


185 


175 


200 


2/0 


195 


215 


200 


230 


3/0 


225 


250 


230 


265 


4/0 


265 


290 


270 


305 


250 


295 


325 


300 


335 


350 


365 


405 


370 


415 


500 


460 


510 


460 


515 


750 


600 


665 


590 


660 


1000 


715 


800 


700 


780 


Relet iu il().60iC)(4) loi the ampacity 


correi lion factor; 


where the 



Table 310.60)0(67) Ampacities of Insulated Single Copper 
Conductor Cables Triplexed in Air Based on Conductor 



rnbient aii f mperatiire i <><Vi than ! «i • (I04°F) 

Table 310.60(0(69) Ampacities of Insulated Single Copper 
Conductor Isolated in Air Based on Conductor Temperatures 
of 90°C (194°F) and 105°C (221°F) and Ambient Air 
Temperature of 40°C (104°F)* 

Temperature Rating of Conductor 
[See Table 310.104(C).] 



Ambient Air Temperature 


of 40°C (104°F)* 






2001-5000 Volts 
Ampacity 


5001-15,000 
Volts Ampacity 


15,001-35,000 
Volts Ampacity 








, .. ,. r , . , 




























[See Table 310.104(C).] 




Conductor 

Size 

(AWG 


90°C 

(194°F) 

Type 


105°C 

(221°F) 
Type 


90°C 

(194 F) 
Type 


105°C 

(221°F) 
Type 


90°C 

(194°F) 

Type 


105°C 




2001-5000 Volts 


5001-35,000 Volts 


(221°F) 
Type 




Ampacity 


Ampacity 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


Conductor 




105°C 




105°C 


8 


83 


93 










Size 


90°C 


(221°F) 


90°C 


(221 °F) 


6 


110 


120 


110 


125 








(AWG 


(194°F) 


Type 


(194°F) 


Type 


4 


145 


160 


150 


165 


— 





or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


2 
1 


190 

225 


215 
250 


195 

225 


215 
250 


225 


— 












250 


8 


65 


74 


— 


— 
















6 


90 


99 


100 


110 


1/0 


260 


290 


260 


290 


260 


290 


4 


120 


130 


130 


140 


2/0 


300 


330 


300 


335 


300 


330 


2 


160 


175 


170 


195 


3/0 


345 


385 


345 


385 


345 


380 


1 


185 


205 


195 


225 


4/0 


400 


445 


400 


445 


395 


445 


1/0 


215 


240 


225 


255 


250 


445 


495 


445 


495 


440 


490 


2/0 


250 


275 


260 


295 


350 


550 


615 


550 


610 


545 


605 


3/0 


290 


320 


300 


340 


500 


695 


775 


685 


765 


680 


755 


4/0 


335 


375 


345 


390 


750 
1000 


900 
1075 


1000 
1200 


885 
1060 


990 
1185 


870 
1040 


970 


250 


375 


415 


380 


430 


1160 


350 


465 


515 


470 


525 


1250 


1230 


1370 


1210 


1350 


1185 


1320 


500 


580 


645 


580 


650 


1500 


1365 


1525 


1 345 


1500 


1315 


1465 


750 


750 


835 


730 


820 


1750 


1495 


1665 


1470 


1640 


1430 


1595 


1000 


880 


980 


850 


950 


2000 


1605 


1790 


1575 


1755 


1535 


1710 



>Pvr ( 10.60(C)(4) for the arnpacit) :orreetion factors where the 
ambient air tompci .nine is other llian 40 C i KMT). 



Refer to 31().60lC)l 1- fo the ampacit; correction factors wheie the 
ambient ai« te nperature • , othei thin) 40"( (H)4 r F) 



70-160 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRTNG 



310.60 



Table 310.611(0(7!)) Ampacities of Insulated Single 
Aluminum Conductor Isolated in Air Based on Conductor 
Temperatures of 90°C (194°F) and 105°C (221 °F) and 
Ambient Air Temperature of 40°C (104°F)* 







Temperature Rating of Conductor 










[See Table 310.104(C).] 






2001-5000 Volts 


5001- 


-15,000 


15,001 


-35,000 




Ampacity 


Volts Ampacity 
90°C 105°C 


Volts A 
90°C 


mpacity 


Conductor 


90°C 


105°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


MV-90 


MV-105 


8 


64 


71 










6 


85 


95 


87 


97 







4 


115 


125 


115 


130 








2 


150 


165 


150 


170 








1 


175 


195 


175 


195 

225 


175 
200 


195 


1/0 


200 


225 


200 


225 


2/0 


230 


260 


235 


260 


230 


260 


3/0 


270 


300 


270 


300 


270 


300 


4/0 


310 


350 


310 


350 


310 


345 


250 


345 


385 


345 


385 


345 


380 


350 


430 


480 


430 


480 


430 


475 


500 


545 


605 


535 


600 


530 


590 


750 


710 


790 


700 


780 


685 


765 


1000 


855 


950 


840 


940 


825 


920 


1250 


980 


1095 


970 


1080 


950 


1055 


1500 


1105 


1230 


1085 


1215 


1060 


1180 


1750 


1215 


1355 


1195 


1335 


1165 


1300 


2000 


1320 


1475 


1295 


1445 


1265 


1410 



Refei to 310.60(C)(4) lor the ampacity correction factors where the 
ambie i'I lii tempei iture is ofhet thai 40V n'M- F) 



Table 310.60(0(71) Ampacities of an Insulated 
Three-Conductor Copper Cable Isolated in Air Based on 
Conductor Temperatures of 90°C (194 C F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F)* 



Temperature Rating of Conductor 
[See Table 310.104(C).] 



Table 310.60(0(72) Ampacities of an Insulated 
Three-Conductor Aluminum Cable Isolated in Air Based on 
Conductor Temperatures of 90°C (194°F) and 105°C (221°F) 
and Ambient Air Temperature of 40°C (104°F)* 







Temperature Rating of Conductor 








[See Table 310.104(C).] 






2001- 


-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 






105°C 




105°C 


Size 


90°C 




(221 °F) 


90° C 


(221 °F) 


(AWG 


(194°F) 




Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


46 




51 






6 


61 




68 


72 


80 


4 


81 




90 


95 


105 


2 


110 




120 


125 


145 


1 


125 




140 


145 


165 


1/0 


145 




160 


170 


185 


2/0 


170 




185 


190 


215 


3/0 


195 




215 


220 


245 


4/0 


225 




250 


255 


285 


250 


250 




280 


280 


315 


350 


310 




345 


345 


385 


500 


385 




430 


425 


475 


750 


495 




550 


540 


600 


1000 


585 




650 


635 


705 



*Refei to 310.60(( >(4) foi the ampacity coi eerion factors where the 
ambien emperaturc i oih.*> u..m 4 ( ' (104°F) 

Table 310.60(0(73) Ampacities of an Insulated Triplexed or 
Three Single-Conductor Copper Cables in Isolated Conduit 
in Air Based on Conductor Temperatures of 90° C (194°F) 
and 105°C (221 °F) and Ambient Air Temperature of 40°C 

(104°F)* 



Temperature Rating of Conductor 
[See Table 310.104(C).] 





2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 


Conductor 

Size 

(AWG 

or kcmil) 


2001-5000 Volts 
Ampacity 


5001-35,000 Volts 
Ampacity 




90°C 
(194°F) 

Type 
MV-90 


105°C 

(221°F) Type 

MV-105 


90°C 

(194°F) 

Type 

MV-90 




Conductor 

Size 

(AWG 


90°C 

(194°F) 

Type MV-90 


105°C 

(221°F) 

Type 
MV-105 


90°C (194°F) 
Type MV-90 


105°C 

(221°F) 

Type 

MV-105 


105°C 

(221°F) Type 
MV-105 


or kcmil) 


8 
6 
4 
2 
1 


55 

75 

97 

130 

155 


61 

84 

110 

145 

175 


83 
110 
150 
170 




8 
6 

4 

2 


59 

79 

105 

140 

160 


66 

88 
115 
154 
180 


93 
120 
165 
185 




105 
135 
185 
210 


93 
120 
165 
190 


1 


1/0 
2/0 
3/0 
4/0 


180 
205 
240 
280 


200 
225 
270 
305 


195 
225 
260 
295 




1/0 
2/0 
3/0 
4/0 


185 
215 
250 
285 


205 
240 
280 
320 


215 
245 
285 
325 




240 
275 
315 
360 


215 
255 
290 
330 


250 
350 
500 
750 
1000 


315 
385 
475 
600 
690 


355 
430 
530 
665 
770 


330 
395 
480 
585 
675 




250 
350 
500 
750 
1000 


320 
395 
485 
615 
705 


355 
440 
545 
685 
790 


360 
435 

535 
670 
770 




400 
490 
600 
745 
860 


365 
440 
535 
655 

755 



*Refer to 310.60(C)(4) for (he ampacity correction factors where the 
ambient air temperature is other than 40 C f K)4 r Ft. 



Rcfei to "id 7K )(4) foi the aj ipai t> collection factors where the 
imbient ait r nperatu . i. otliei rbiii 4 ) C i 104 F) 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-161 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.60(0(74) Ampacities of an Insulated Triplexed or 
Three Single-Conductor Aluminum Cables in Isolated 
Conduit in Air Based on Conductor Temperatures of 90°C 
(194°F) and 105°C (221 °F) and Ambient Air Temperature of 
40°C (104°F)* 



Table 310.60(0(76! Ampacities of an Insulated 
Three-Conductor Aluminum Cable in Isolated Conduit in 
Air Based on Conductor Temperatures of 90°C (194°F) and 
105°C (221 °F) and Ambient Air Temperature of 40°C 

(104°F)* 





Temperature Rating of Conductor 
[See Table 310.104(C).] 






Temperature Rating of Conductor 
[See Table 310.104(C).] 




2001-5000 Volts 


5001-35,000 Volts 


2001- 


-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 






10S°C 




105°C 






105°C 




105°C 


Conductor 


90°C 


(221°F) 


90°C 


(221°F) 


Size 


90°C 




(221 °F) 


90°C 


(221°F) 

Type 
MV-105 


Size (AWG 
or kcmil) 


(194°F) 
Type MV-90 


Type 
MV-105 


(194°F) 
Type MV-90 


Type 
MV-105 


(AWG 
or kcmil) 

8 
6 
4 
2 
1 


(194°F) 
Type MV-90 


Type 
MV-105 


(194°F) 
Type MV-90 


8 
6 

4 
2 
1 


43 
58 
76 
100 
120 


48 
65 
85 
115 
135 


65 

84 

115 

130 


72 

94 

130 

150 


41 
53 
71 
96 
110 




46 

59 
79 
105 
125 


64 

84 

115 

130 


71 

94 

125 

145 


1/0 
2/0 
3/0 
4/0 


140 
160 
190 
215 


155 
175 
210 
240 


150 
175 
200 
230 


170 
200 
225 
260 


1/0 
2/0 
3/0 
4/0 

250 


130 
150 
170 
200 




145 
165 
190 
225 


150 

170 
195 

225 


170 
190 
220 
255 


250 


250 


280 


255 


290 


220 




245 


250 


280 


350 

500 

750 

1000 


305 
380 
490 
580 


340 

425 
545 
645 


310 
385 
485 
565 


350 
430 
540 
640 


350 

500 

750 

1000 


275 
340 
430 
505 




305 
380 
480 
560 


305 

380 
470 
550 


340 
425 
520 
615 



•'Refer to 310.60(C)(4) for the ampacity correction factors where the 
ambient air temperature is other than 40°C ( I04"F). 



Refer to 310.60(C)(4) for the ampacity correction factors, where the 
ambient air temperature is other than 40"C (104°F). 



Table 310.60(0(75) Ampacities of an Insulated 
Three-Conductor Copper Cable in Isolated Conduit in Air 
Based on Conductor Temperatures of 90°C (194°F) and 
105°C (221°F) and Ambient Air Temperature of 40°C 
(104°F)* 





Temperature Rating of Conductor 








[See Table 310.104(C).] 






2001-5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 




105°C 




105°C 


Size 


90°C 


(221°F) 


90°C 


(221°F) 


(AWG 


(194°F) 


Type 


(194°F) 


Type 


or kcmil) 


Type MV-90 


MV-105 


Type MV-90 


MV-105 


8 


52 


58 


^_ 


__ 


6 


69 


77 


83 


92 


4 


91 


100 


105 


120 


2 


125 


135 


145 


165 


1 


140 


155 


165 


185 


1/0 


165 


185 


195 


215 


'VO 


190 


210 


220 


245 


3/0 


220 


245 


250 


280 


4/0 


255 


285 


290 


320 


250 


280 


315 


315 


350 


350 


350 


390 


385 


430 


500 


425 


475 


470 


525 


750 


525 


585 


570 


635 


1000 


590 


660 


650 


725 



Refer to 310.60(C)(4) lor the ampa it> c >rr< c »>n factors where the 
ambient air temperature is othei than 40 C (104 3 F). 



70-162 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.60 



Table 310.60(0(77) Ampacities of Three Single-Insulated 
Copper Conductors in Underground Electrical Ducts (Three 
Conductors per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement in 
'..■ t ,>:*•.; with Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
of 90°C (194°F) and 105°C (221°F) 



Table 310.60(C)(7H) Ampacities of Three Single-Insulated 
Aluminum Conductors in Underground Electrical Ducts 
(Three Conductors per Electrical Duct) Based on Ambient 
Earth Temperature of 20 C (68°F), Electrical Duct 
Arrangement in W • lance with Figure 310.60, 100 Percent 
Load Factor, Thermal Resistance (RHO) of 90, Conductor 
Temperatures of 90°C (194°F) and 105°C (221°F) 



Temperature Rating of Conductor 
[See Table 310.104(C).] 



Temperature Rating of Conductor 
[See Table 310.104(C).] 



2001-5000 Volts 
Ampacity 



5001-35,000 Volts 
Ampacity 



2001-5000 Volts 
Ampacity 



Conductor 
Size 

(AWG 
or kcmil) 



90°C 

(194°F) 

Type 

MV-90 



105°C 

(221°F) 

Type 
MV-105 



90°C 
(194°F) 

Type 
MV-90 



105°C 
(221°F) 

Type 
MV-105 



Conductor 

Size 

(AWG 

or kcmil) 



90°C 
(194°F) 

Type 
MV-90 



105°C 

(221°F) 

Type 
MV-105 



One Circuit (See Figure 
310.60, Detail 1.) 



Three Circuits (See Figure 
310.60, Detail 2.) 



Six Circuits (See Figure 
310.60, Detail 3.) 



One Circuit (See Figure 
310.60, Detail 1.) 



Three Circuits (See Figure 
310.60, Detail 2.) 



Six Circuits (See Figure 
310.60, Detail 3.) 



5001-35,000 Volts 
Ampacity 



90°C 

(194°F) 

Type 

MV-90 



105°C 

(221°F) 

Type 
MV-105 



8 


64 


69 


— 


— 


8 


50 


54 


— 


— 


6 


85 


92 


90 


97 


6 


66 


71 


70 


75 


4 


110 


120 


115 


125 


4 


86 


93 


91 


98 


2 


145 


155 


155 


165 


2 


115 


125 


120 


130 


1 


170 


180 


175 


185 


1 


130 


140 


135 


145 


1/0 


195 


210 


200 


215 


1/0 


150 


160 


155 


165 


2/0 


220 


235 


230 


245 


2/0 


170 


185 


175 


190 


3/0 


250 


270 


260 


275 


3/0 


195 


210 


200 


215 


4/0 


290 


310 


295 


315 


4/0 


225 


245 


230 


245 


250 


320 


345 


325 


345 


250 


250 


270 


250 


270 


350 


385 


415 


390 


415 


350 


305 


325 


305 


330 


500 


470 


505 


465 


500 


500 


370 


400 


370 


400 


750 


585 


630 


565 


610 


750 


470 


505 


455 


490 


1000 


670 


720 


640 


690 


1000 


545 


590 


525 


565 



8 


56 


60 


— 





8 


44 


47 


— 


— 


6 


73 


79 


77 


83 


6 


57 


61 


60 


65 


4 


95 


100 


99 


105 


4 


74 


80 


77 


83 


2 


125 


130 


130 


135 


2 


96 


105 


100 


105 


1 


140 


150 


145 


155 


1 


110 


120 


110 


120 


1/0 


160 


175 


165 


175 


1/0 


125 


135 


125 


140 


2/0 


185 


195 


185 


200 


2/0 


145 


155 


145 


155 


3/0 


210 


225 


210 


225 


3/0 


160 


175 


165 


175 


4/0 


235 


255 


240 


255 


4/0 


185 


200 


185 


200 


250 


260 


280 


260 


280 


250 


205 


220 


200 


220 


350 


315 


335 


310 


330 


350 


245 


265 


245 


260 


500 


375 


405 


370 


395 


500 


295 


320 


290 


315 


750 


460 


495 


440 


475 


750 


370 


395 


355 


385 


1000 


525 


565 


495 


535 


1000 


425 


460 


405 


440 



8 


48 


52 


— 


— 


8 


38 


41 


— 


— 


6 


62 


67 


64 


68 


6 


48 


52 


50 


54 


4 


80 


86 


82 


88 


4 


62 


67 


64 


69 


2 


105 


110 


105 


115 


2 


80 


86 


80 


88 


1 


115 


125 


120 


125 


1 


91 


98 


90 


99 


1/0 


135 


145 


135 


145 


1/0 


105 


110 


105 


110 


2/0 


150 


160 


150 


165 


2/0 


115 


125 


115 


125 


3/0 


170 


185 


170 


185 


3/0 


135 


145 


130 


145 


4/0 


195 


210 


190 


205 


4/0 


150 


165 


150 


160 


250 


^10 


225 


210 


225 


250 


165 


180 


165 


175 


350 


250 


270 


245 


265 


350 


195 


210 


195 


210 


500 


300 


325 


290 


310 


500 


240 


255 


230 


250 


750 


365 


395 


350 


375 


750 


290 


315 


280 


305 


1000 


410 


445 


390 


415 


1000 


335 


360 


320 


345 


2011 Edition 


NATIONAL ELECTRICAL CODE 














70-163 



310.60 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.60(0(79) Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement in 
Accordance with Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
of 90°C (194°F) and 105°C (221°C) 



Table 310.60(0(80) Ampacities of Three Insulated 
Aluminum Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable) in Underground Electrical Ducts 
(One Cable per Electrical Duct) Based on Ambient Earth 
Temperature of 20°C (68°F), Electrical Duct Arrangement in 
A . , . ; i.> it ,: with Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
of 90°C (194°F) and 105°C (221°C) 





Temperature Rating of Conductor 




Temperature Rating of Conductor 






[See Table 310.104(C).] 








[See Table 310.104(C).) 






2001-5000 Volts 


5001-35,000 Volts 


2001-! 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Figure 








One Circuit (See Figure 








310.60, Detail 1.) 










310.60, Detail 1.) 










8 


59 


64 





_— 


8 


46 


50 


_ 




6 


78 


84 


88 


95 


6 


61 


66 


69 


74 


4 


100 


110 


115 


125 


4 


80 


86 


89 


96 


2 


135 


145 


150 


160 


2 


105 


110 


115 


125 


1 


155 


165 


170 


185 


1 


120 


130 


135 


145 


I/O 


175 


190 


195 


210 


1/0 


140 


150 


150 


165 


2/0 


200 


220 


220 


235 


2/0 


160 


170 


170 


185 


3/0 


230 


250 


250 


270 


3/0 


180 


195 


195 


210 


4/0 


265 


285 


285 


305 


4/0 


205 


220 


220 


240 


250 


290 


315 


310 


335 


250 


230 


245 


245 


265 


350 


355 


380 


375 


400 


350 


280 


310 


295 


315 


500 


430 


460 


450 


485 


500 


340 


365 


355 


385 


750 


530 


570 


545 


585 


750 


425 


460 


440 


475 


1000 


600 


645 


615 


660 


1000 


495 


535 


510 


545 


Three Circuits (See 


Figure 








Three Circuits (See 


Figure 








310.60, Detail 2.) 










310.60, Detail 2.) 










8 


53 


57 








8 


41 


44 






6 


69 


74 


75 


81 


6 


54 


58 


59 


64 


4 


89 


96 


97 


105 


4 


70 


75 


75 


81 


2 


115 


125 


125 


135 


2 


90 


97 


100 


105 


7 


135 


145 


140 


155 


1 


105 


110 


110 


120 


1/0 


150 


165 


160 


175 


1/0 


120 


125 


125 


135 


2/0 


170 


185 


185 


195 


2/0 


135 


145 


140 


155 


3/0 


195 


210 


205 


220 


3/0 


155 


165 


160 


175 


4/0 


225 


240 


230 


250 


4/0 


175 


185 


180 


195 


250 


245 


265 


255 


270 


250 


190 


205 


200 


215 


350 


295 


315 


305 


325 


350 


230 


250 


240 


755 


500 


355 


380 


360 


385 


500 


280 


300 


285 


305 


750 


430 


465 


430 


465 


750 


345 


375 


350 


375 


1000 


485 


520 


485 


515 


1000 


400 


430 


400 


430 


Six Circuits (See Figure 








Six Circuits (See Figure 








310.60, Detail 3.) 










310.60, Detail 3.) 










8 


46 


50 








8 


36 


39 






6 


60 


65 


63 


68 


6 


46 


50 


49 


53 


4 


77 


83 


81 


87 


4 


60 


65 


63 


68 


2 


98 


105 


105 


no 


2 


77 


83 


80 


86 


1 


110 


120 


115 


125 


1 


87 


94 


90 


98 


1/0 


125 


135 


130 


145 


1/0 


99 


105 


105 


110 


2/0 


145 


155 


150 


160 


2/0 


110 


120 


115 


125 


3/0 


165 


175 


170 


180 


3/0 


130 


140 


130 


140 


4/0 


185 


200 


190 


200 


4/0 


145 


155 


150 


160 


250 


200 


220 


205 


220 


250 


160 


170 


160 


170 


350 


240 


270 


245 


275 


350 


190 


205 


190 


205 


500 


290 


310 


290 


305 


500 


230 


245 


230 


245 


750 


350 


375 


340 


365 


750 


280 


305 


275 


295 


1000 


390 


420 


380 


405 


1000 


320 


345 


315 


335 



70-164 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.104 



Table 310.60(C)(8)) Ampacities of Single Insulated Copper 
Conductors Directly Buried in Earth Based on Ambient 
Earth Temperature of 20°C (68°F), Arrangement per Figure 
310.60, 100 Percent Load Factor, Thermal Resistance (RHO) 
of 90, Conductor Temperatures of 90°C (194°F) and 105°C 
(221°C) 



Table 310.60(( )(S2) Ampacities of Single Insulated 
Aluminum Conductors Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 





Temperature Ratint 


; of Conductor 




Temperature Rati 


ing of Conductor 






[See Table 310.104(C).] 








[See Table 310.104(C).] 






2001-5000 Volts 


5001-35,000 Volts 


2001 -i 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221 °F) 


(194°F) 


(221 °F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 . 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit, 










One Circuit, Three 










Three Conductors (See 








Conductors (See Figure 








Figure 










310.60, Detail 9.) 










310.60, Detail 9.) 






























8 


85 


90 


— 


— 


8 


110 


115 








6 


110 


115 


100 


110 


6 


140 


150 


130 


140 


4 


140 


150 


130 


140 


4 


180 


195 


170 


180 


2 


ISO 


195 


165 


175 


2 


230 
260 


250 
280 


210 
240 


225 
260 


1 


205 


220 


185 


200 


1 










230 












1/0 


230 


250 


215 


1/0 


295 


320 


275 


295 


2/0 


265 


285 


245 


260 


2/0 


335 


365 


310 


335 


3/0 


300 


320 


275 


295 


3/0 


385 
435 


415 
465 


355 
405 


380 
435 


4/0 


340 


365 


315 


340 


4/0 










370 












250 


370 


395 


345 


750 


470 


510 


440 


475 


350 


445 


480 


415 


450 


350 


570 


615 


535 


575 


500 


540 


580 


510 


545 


500 


690 


745 


650 


700 


750 


665 


720 


635 


680 


750 


845 
980 


910 

1055 


805 
930 


865 
1005 


1000 


780 


840 


740 


795 


1000 






















Two Circuits, Six 










Two Circuits, 










Conductors (See J 


Figure 








Six Conductors (S 


ee Figure 








310.60, Detail 10.) 








310.60, Detail 10.) 










8 


80 


85 






8 


100 


110 








6 


100 


110 


95 


100 


6 


130 


140 


120 


130 


4 


130 


140 


125 


130 


4 


165 


180 


160 


170 


2 


165 


ISO 


155 


165 


2 


215 
240 


230 
260 


195 
225 


210 
240 


1 


190 


200 


175 


190 


1 










215 












1/0 


215 


230 


200 


1/0 


275 


o 95 


755 


275 


2/0 


245 


260 


225 


245 


2/0 


310 


335 


790 


315 


3/0 


275 


295 


255 


275 


3/0 


355 
400 


380 
430 


330 
375 


355 
405 


4/0 


310 


335 


290 


315 


4/0 






















250 


340 


365 


320 


345 


250 


435 


470 


410 


440 


350 


410 


440 


385 


415 


350 


520 


560 


495 


530 


500 


495 


530 


470 


505 


500 


630 


680 


600 


645 


750 


610 


655 


580 


625 


750 


775 


835 


740 


795 


1000 


710 


765 


680 


730 


1000 


890 


960 


855 


920 













201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-165 



310.104 



ARTICLE 310 ~ CONDUCTORS FOR GENERAL WIRING 



Table 310.60(0(83) Ampacities of Three Insulated Copper 
Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 



Table 310.60(0(84) Ampacities of Three Insulated 
Aluminum Conductors Cabled Within an Overall Covering 
(Three-Conductor Cable), Directly Buried in Earth Based on 
Ambient Earth Temperature of 20°C (68°F), Arrangement 
per Figure 310.60, 100 Percent Load Factor, Thermal 
Resistance (RHO) of 90, Conductor Temperatures of 90°C 
(194°F) and 105°C (221°F) 





Temperature Ratinj 


I of Conductor 




Temperature Rating of Conductor 






[See Table 310.104(C).] 








[See Table 310.104(C).] 






2001-5000 Volts 


5001-35,000 Volts 


2001-: 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(22FF) 


(194°F) 


(221°F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit (See Figure 








One Circuit (See Figure 








310.60, Detail 5.) 










310.60, Detail 5.) 










8 


85 


89 








8 


65 


70 






6 


105 


115 


115 


120 


6 


80 


88 


90 


95 


4 


135 


150 


145 


155 


4 


105 


115 


115 


125 


2 


180 


190 


185 


200 


2 


140 


150 


145 


155 


1 


200 


215 


210 


225 


1 


155 


170 


165 


175 


1/0 


230 


245 


240 


255 


1/0 


180 


190 


185 


200 


2/0 


260 


280 


270 


290 


2/0 


205 


220 


210 


225 


3/0 


295 


320 


305 


330 


3/0 


230 


250 


240 


260 


4/0 


335 


360 


350 


375 


4/0 


260 


280 


270 


295 


250 


365 


395 


380 


410 


250 


285 


310 


300 


320 


350 


440 


475 


460 


495 


350 


345 


375 


360 


390 


500 


530 


570 


550 


590 


500 


420 


450 


435 


470 


750 


650 


700 


665 


720 


750 


520 


560 


540 


580 


1000 


730 


785 


750 


810 


1000 


600 


650 


620 


665 


Two Circuits (See Figure 








Two Circuits (See Figure 








310.60, Detail 6.) 










310.60, Detail 6.) 










8 


so 


84 








8 


60 


66 






6 


100 


105 


105 


115 


6 


75 


83 


80 


95 


4 


130 


140 


135 


145 


4 


100 


no 


105 


115 


2 


165 


180 


170 


185 


2 


130 


140 


135 


145 


1 


185 


200 


195 


210 


1 


145 


155 


150 


165 


1/0 


215 


230 


220 


235 


1/0 


165 


180 


170 


185 


2/0 


240 


260 


250 


270 


2/0 


190 


205 


195 


210 


3/0 


275 


295 


280 


305 


3/0 


215 


230 


270 


240 


4/0 


310 


335 


320 


345 


4/0 


245 


260 


250 


270 


250 


340 


365 


350 


375 


250 


265 


285 


275 


295 


350 


410 


440 


420 


450 


350 


320 


345 


330 


355 


500 


490 


525 


500 


535 


500 


385 


415 


395 


425 


750 


595 


640 


605 


650 


750 


480 


515 


485 


525 


1000 


665 


715 


675 


730 


1000 


550 


590 


560 


600 



70-166 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.104 



Table 310.60(Ci(8f I Ampacities of Three Triplexed Single 
Insulated Copper Conductors Directly Buried in Earth 
Based on Ambient Earth Temperature of 20°C (68°F), 
Arrangement per Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
90°C (194°F) and 105°C (221°F) 



Table 310.60(0(86) Ampacities of Three Triplexed Single 
Insulated Aluminum Conductors Directly Buried in Earth 
Based on Ambient Earth Temperature of 20°C (68°F), 
Arrangement per Figure 310.60, 100 Percent Load Factor, 
Thermal Resistance (RHO) of 90, Conductor Temperatures 
90°C (194°F) and 105°C (221°F) 





Temperature Rating of Conductor 




Temperature Rating of Conductor 






[See Table 310.104(C).] 








[See Table 310.104(C).] 






2001-: 


5000 Volts 


5001-35,000 Volts 


2001-! 


5000 Volts 


5001-35,000 Volts 




Ampacity 


Ampacity 


Conductor 


Ampacity 


Ampacity 


Conductor 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


90°C 


105°C 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


Size 


(194°F) 


(221°F) 


(194°F) 


(221°F) 


(AWG 


Type 


Type 


Type 


Type 


(AWG 


Type 


Type 


Type 


Type 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


or kcmil) 


MV-90 


MV-105 


MV-90 


MV-105 


One Circuit, Three 










One Circuit, Three 










Conductors (See Figure 








Conductors (See Figure 








310.60, Detail 7.) 










310.60, Detail 7.) 










8 


90 


95 








8 


70 


75 






6 


120 


130 


115 


120 


6 


90 


100 


90 


95 


4 


150 


165 


150 


160 


4 


120 


130 


115 


125 


2 


195 


205 


190 


205 


2 


155 


165 


145 


155 


1 


225 


240 


215 


230 


1 


175 


190 


165 


175 


1/0 


255 


270 


245 


260 


1/0 


200 


210 


190 


205 


2/0 


290 


310 


275 


295 


2/0 


225 


240 


215 


230 


3/0 


330 


360 


315 


340 


3/0 


255 


275 


245 


265 


4/0 


375 


405 


360 


385 


4/0 


290 


310 


280 


305 


250 


410 


445 


390 


410 


250 


320 


350 


305 


325 


350 


490 


580 


470 


505 


350 


385 


420 


370 


400 


500 


590 


635 


565 


605 


500 


465 


500 


445 


480 


750 


725 


780 


685 


740 


750 


580 


625 


550 


590 


1000 


825 


885 


770 


830 


1000 


670 


725 


635 


680 


Two Circuits, Six 










Two Circuits, Six 










Conductors (See Figure 








Conductors (See Figure 








310.60, Detail 8.) 










310.60, Detail 8.) 










8 


85 


90 








8 


65 


70 


__ 


_ 


6 


110 


115 


105 


115 


6 


85 


95 


85 


90 


4 


140 


150 


140 


150 


4 


110 


120 


105 


115 


2 


180 


195 


175 


190 


2 


140 


150 


135 


145 


1 


205 


220 


200 


215 


1 


160 


170 


155 


170 


1/0 


235 


250 


225 


240 


1/0 


180 


195 


175 


190 


2/0 


265 


285 


255 


275 


2/0 


205 


220 


200 


215 


3/0 


300 


320 


290 


315 


3/0 


235 


250 


225 


245 


4/0 


340 


365 


325 


350 


4/0 


265 


285 


255 


275 


250 


370 


395 


355 


380 


250 


290 


310 


280 


300 


350 


445 


480 


425 


455 


350 


350 


375 


335 


360 


500 


535 


575 


510 


545 


500 


420 


455 


405 


435 


750 


650 


700 


615 


660 


750 


520 


560 


485 


525 


1000 


740 


795 


690 


745 


1000 


600 


645 


565 


605 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-167 



310.104 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



III. Construction Specifications 

310.104 Conductor Constructions and Applications. In- 
sulated conductors shall comply with the applicable provi- 
sions of Table 3IO.J04fA) through Table 310.104(E). 



Informational Note: Thermoplastic insulation may stiffen 
at temperatures lower than -10°C (+14°F). Thermoplastic 
insulation may also be deformed at normal temperatures 
where subjected to pressure, such as at points of support. 
Thermoplastic insulation, where used on dc circuits in wet 
locations, may result in electroendosmosis between con- 
ductor and insulation. 



Table 310.104(A) Conductor Applications and Insulations Rated 600 Volts 







Maximum 
Operating 






Thickness of Insulation 














Trade Name 


Type Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering 1 


Fluorinated 


FEPor 


90°C 


Dry and damp locations 


Fluorinated ethylene 


14-10 


0.51 


20 


None 


ethylene 


FEPB 


I94°F 




propylene 


8-2 


0.76 


30 




propylene 














200°C 
392°F 


Dry locations — special 
applications 2 


Fluorinated ethylene 
propylene 


14-8 


0.36 


14 


Glass braid 






















6-2 


0.36 


14 


Glass or other suitable 
braid material 


Mineral insulation 


Ml 


90°C 


Dry and wet locations 


Magnesium oxide 


18-I6 3 


0.58 


23 


Copper or alloy steel 


(metal sheathed) 




194°F 






16-10 


0.91 


36 








250°C 


For special applications" 




9-4 


1.27 


50 








482°F 






3-500 


1.40 


55 




Moisture-, heat-, 


MTW 


60°C 


Machine tool wiring in 


Flame-retardant, 




(A) (B) 


(A) (B) 


(A) None 


and oil-resistant 




140°F 


wet locations 


moisture-, heat-, and 
oil-resistant 








(B) Nylon jacket or 


thermoplastic 






equivalent 






90 ">C 


Machine tool wiring in 


thermoplastic 


22-12 


0.76 038 


30 15 








194°F 


dry locations. 
Informational Note: See 
NFPA 79. 




10 

8 

6 

4-2 

1-4/0 

213-500 

501-1000 


0.76 0.51 
1.14 0.76 
1.52 0.76 
1.52 1.02 

2.03 1.27 
2.41 1.52 
2.79 1.78 


30 20 
45 3d 
60 30 
60 40 
80 50 
95 60 
110 70 




Paper 




85"C 
185°F 


For underground service 
conductors, or by special 
permission 


Paper 








Lead sheath 


Perfluoro-alkoxy 


PFA 


90°C 
194°F 


Dry and damp locations 


Perfluoro-alkoxy 


14-10 

8-2 


0.51 
0.76 


20 
30 


None 






200°C 


Dry locations — special 




1-V0 


1.14 


45 








392°F 


applications 2 












Perfluoro-alkoxy 


PFAH 


250°C 


Dry locations only. Only 


Perfluoro-alkoxy 


14-10 


0.51 


20 


None 






482°F 


for leads within apparatus 
or within raceways 
connected to apparatus 
(nickel or nickel-coated 
copper only) 




8-2 
1-4/0 


0.76 
1.14 


30 
45 




Thermoset 


RHH 


90°C 


Dry and damp locations 




14-10 


1.14 


45 


Moisture -resistant, 






194°F 






8-2 

1—4/0 

213-500 

501-1000 

1001-2000 


1.52 
2.03 
2.41 
2.79 
3.18 


60 
80 
95 
110 
125 


flame-retardant, 
nonmetallic covering 1 


Moisture- 


RHW 


75°C 


Dry and wet locations 


Flame-retardant, 


14-10 


1.14 


45 


Moisture-resistant, 


resistant 




I67°F 




moisture- 


8-2 


1.52 


60 


tlame-retardant, 










resistant thermoset 


1-4/0 
213-500 


2.03 
2.41 


80 
95 


nonmetallic. coveting 












RHW-2 


90°C 
I94°F 






501-1000 


2.79 


no 












1001-2000 


3.18 


125 




Silicone 


SA 


90°C 


Drv and damp locations 


Silicone rubber 


14-10 


1.14 


45 


Glass or other suitable 






194°F 






8-2 
I-4V0 


1.52 
2.03 


60 
80 


braid material 






200°C 


For special application 2 




213-500 


2.41 


95 








392°F 






501-1000 
1001-2000 


2.79 
3.18 


110 

125 





70-168 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.104 



Table 310.104(A) Continued 







Maximum 






Thickness of Insulation 








Operating 
























Trade Name 


Type Letter 


Temperature 


Application Provisions 


Insulation 


AWG or kcmil 


mm 


mils 


Outer Covering' 


Thermoset 


SIS 


90°C 


Switchboard wiring only 


Flame-retardant 


14-10 


0.76 


30 


None 






I94°F 




thermoset 


8-2 
1-4/0 


1.14 
2.41 


45 

55 




Thermoplastic and 


TBS 


90°C 


Switchboard wiring only 


Thermoplastic 


14-10 


0.76 


30 




fibrous outer braid 




194°F 






8 
6-2 
1-4/0 


1.14 

1.52 
2.03 


45 
60 
80 


nonmetallic covering 


Extended polytetra- 


TFE 


250°C 


Dry locations only. Only 


Extruded polytetra- 


14-10 


0.51 


20 


None 


fluoro- 




482°F 


for leads within apparatus 


fluoroethylene 


8-2 


0.76 


30 




elhylene 






or within raceways 
connected to apparatus, or 
as open wiring (nickel or 
nickel-coated copper only) 




1-4/0 


1.14 


45 




Heat-resistant 


THHN 


90°C 


Dry and damp locations 


Flame-retardant, 


14-12 


0.38 


15 


Nylon jacket or 


thermoplastic 




194°F 




heat-resistant 
thermoplastic 


10 

8-6 

4-2 

1-1/0 

250-500 

501-1000 


0.51 
0.76 
1.02 

1.27 
1.52 
1.78 


20 
30 
40 
50 
60 
70 


equivalent 


Moisture- and 


THHW 


75°C 


Wet location 


Flame-retardant, 


14-10 


0.76 


30 




heat-resistant 




167-F 




moisture- and 


8 


1.14 


45 




thermoplastic 








heat-resistant 


6-2 


1.52 


60 








90°C 


Dry location 


thermoplastic 


1-4/0 


2.03 


80 








I94°F 






213-500 
501-1000 
1001-2000 


2.41 
2.79 
3.18 


95 
110 

125 




Moisture- and 


THW 


75°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


heat-resistant 




I67°F 




moisture- and 


8 


1.14 


45 




thermoplastic 




90°C 


Special applications within 


heat-resistant 


6-2 


1.52 


60 








I94°F 


electric discharge lighting 
equipment. Limited to 
1 000 open-circuit volts or 
less, (size 14-8 only as 
permitted in 410.68) 


thermoplastic 


1-4/0 
213-500 
501-1000 
1001-2000 


2.03 
2.41 
2.79 
3.18 


80 
95 
110 

125 






THW-2 


90°C 


Dry and wet locations 








194°F 














Moisture- and 


THWN 


75°C 


Dry and wet locations 


Flame-retardant, 


14-12 


0.38 


15 


Nylon jacket or 


heat-resistant 




167°F 




moisture- and 


10 


0.51 


20 


equivalent 


thermoplastic 








heat-resistant 
thermoplastic 


8-6 

4-2 


0.76 
1.02 


30 
40 














THWN-2 


90°C 
I94°F 






1-4/0 
250-500 
501-1000 


1.27 
1.52 
1.78 


50 
60 
70 




Moisture- 


TW 


60°C 


Dry and wet locations 


Flarne-retardant, 


14-10 


0.76 


30 


None 


resistant 




140°F 




moisture- 


8 


1.14 


45 




thermoplastic 








resistant 
thermoplastic 


6-2 

1-4/0 

213-500 

501-1000 

1001-2000 


1.52 
2.03 
2.41 
2.79 
3.18 


60 
80 
95 
110 
125 




Underground feeder 


UF 


60°C 


See Article 340. 


Vloisture- 


14-10 


1.52 


60 4 


Integral with insulation 


and branch-circuit 




140°F 




resistant 


8-2 


2.03 


80* 




cable — single 










1-4/0 


2.41 


95 4 




conductor (for 


















Type UF cable 




75°C 














employing more 
than one 




I67°F 5 




leat-resistant 










conductor, see 


















Article 340.) 



















(Continues) 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-169 



310.104 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.104(A) Continued 





Type Letter 


Maximum 

Operating 

Temperature 


Application Provisions 


Insulation 


Thickness of Insulation 




Trade Name 


AWG or kcmil 


mm 


mils 


Outer Covering 1 




USE 


75°C 


See Article 338. 


Heat- and 


14-10 


1.14 


45 


vloisture-resistant 


service- 




1 67°F 5 




moisture-resistant 


8-2 


1.52 


60 


nonmetallic covering 










1-4/0 


2.03 


80 


(See 338.2.) 


single conductor 










213-500 


2.41 


95 6 




(for Type USE 










501-1000 


2.79 


110 




cable employing 










1001-2000 


3.18 


125 




more than one 


















conductor, see 


















Article 338.) 




















USE-2 


90°C 


Dry and wet locations 








194°F 














Thermoset 


XHH 


90°C 


Dry and damp locations 


Flame-retardant 


14-10 


0.76 


30 


None 






194°F 




thermoset 


8-2 

1-4/0 
213-500 
501-1000 
1001-2000 


1.14 
1.40 
1.65 
2.03 
2.41 


45 
55 
65 
80 
95 




Moisture- 


XHHW 


90°C 


Dry and damp locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


resistant 




194°F 




moisture- 


8-2 


1.14 


45 




thermoset 




75°C 
167°F 


Wet locations 


resistant thermoset 


1-4/0 
213-500 
501-1000 
1001-2000 


1.40 
1.65 

2.03 
2.41 


55 
65 
80 
95 




Moisture- 


XHHW-2 


90°C 


Dry and wet locations 


Flame-retardant, 


14-10 


0.76 


30 


None 


resistant 




194°F 




moisture- 


8-2 


1.14 


45 




thermoset 








resistant thermoset 


1-4/0 
213-500 
501-1000 
1001-2000 


1.40 
1.65 

2.03 
2.41 


55 
65 
80 
95 




Modified ethylene 


Z 


90°C 


Dry and damp locations 


Modified ethylene 


14-12 


0.38 


15 


None 


tetrafluoro- 




194°F 




tetrafluoro- 


10 


0.51 


20 




ethvlene 




150°C 


Dry locations — special 


ethylene 


8-4 


0.64 


25 








302°F 


applications 2 




3-1 
1/0-4/0 


0.89 
1.14 


35 
45 




Modified ethylene 


ZW 


75 °C 


Wet locations 


Modified ethylene 


14-10 


0.76 


30 


None 


tetrafluoro- 




167°F 




tetrafluoro- 


8-2 


1.14 


45 




ethylene 




90°C 
194°F 
150°C 
302°F 


Dry and damp locations 

Dry locations — special 
applications 2 


ethylene 












ZW-2 


90°C 


Dry and wet locations 








194°F 















1 Some insulations do not require an outer covering. 

2 Where design conditions require maximum conductor operating temperatures above 90°C (194°F). 

3 For signaling circuits permitting 300-volt insulation. 

• 

4 Includes integral jacket. 

5 For ampacity limitation, see 340.80. 

6 Insulation thickness shall be permitted to be 2.03 mm (80 mils) for listed Type USE conductors that have 
been subjected to special investigations. The nonmetallic covering over individual rubber-covered conduc- 
tors of aluminum-sheathed cable and of lead-sheathed or multiconductor cable shall not be required to be 
flame retardant. For Type MC cable, see 330.104. For nonmetallic-sheathed cable, see Article 334, Part III. 
For Type UF cable, see Article 340, Part III. 



70-170 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



310.106 



Table 310.104(B) Thickness of Insulation for Nonshielded 
Types RHH and RHW Solid Dielectric Insulated Conductors 
Rated 2000 Volts 



Conductor Size 


Column A 1 


Column B 2 










(AWG or kcmil) 


mm 


mils 


mm 


mils 


14-10 


2.03 


80 


1.52 


60 


8 


2.03 


80 


1.78 


70 


6-2 


2.41 


95 


1.78 


70 


1-2/0 


2.79 


110 


2.29 


90 


3/0-4/0 


2.79 


110 


2.29 


90 


213-500 


3.18 


125 


2.67 


105 


501-1000 


3.56 


140 


3.05 


120 


1001-2000 


3.56 


140 


3.56 


140 



'Column A insulations are limited to natural, SBR, and butyl rubbers. 
2 Column B insulations are materials such as cross-linked polyethyl- 
ene, ethylene propylene rubber, and composites thereof. 



310.106 Conductors. 

(A) Minimum Size of Conductors. The minimum size of 
conductors shall be as shown in Table 310.166(A), except 
as permitted elsewhere in this Code. 

(B) Conductor Material. Conductors in this article shall 
be of aluminum, copper-clad aluminum, or copper unless 
otherwise specified. 

Solid aluminum conductors 8, 10, and 12 AWG shall be 
made of an AA-8000 series electrical grade aluminum alloy 
conductor material. Stranded aluminum conductors 8 AWG 
through 1000 kcmil marked as Type RHH, RHW, XHHW, 
THW, THHW, THWN, THHN, service-entrance Type SE 
Style U and SE Style R shall be made of an AA-8000 series 
electrical grade aluminum alloy conductor material. 



Table 310.104(C) Conductor Application and Insulation Rated 2001 Volts and Higher 



Trade 
Name 



Maximum Operating Application 

Type Letter Temperature Provision 



Insulation 



Outer Covering 



Medium voltage solid MV-90 

dielectric MV-105* 



90°C Dry or wet locations Thermo- Jacket, sheath, or 

105°C plastic or thermo- armor 

setting 



*Where design conditions require maximum conductor temperatures above 90 C C. 



Table 310.104(D) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated Conductors Rated 2001 to 5000 
Volts 









Dry Locations, Single Conductor 








Wet or Dry Locations 








Without 




With Jacket 






Single Conductor 












Jacket 


















Vlulticon 




























Insulation 


Insulation 


Jacket 


Insulation 


Jacket 


Insulation* 


Conductor size 


























(AWG or kcmil) 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


, 


S 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


i 


5 


2.79 


110 


2.29 


90 


0.76 


30 


3.18 


125 


2.03 


80 


2.29 


90 


4- 


-2 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


1- 


2/0 


2.79 


110 


2.29 


90 


1.14 


45 


3.18 


125 


2.03 


80 


2.29 


90 


3AM/0 


2.79 


110 


2.29 


90 


1.65 


65 


3.18 


125 


2.41 


95 


2.29 


90 


213 


-500 


3.05 


120 


2.29 


90 


1.65 


65 


3.56 


140 


2.79 


110 


2.29 


90 


501 


-750 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 


751- 


-1000 


3.30 


130 


2.29 


90 


1.65 


65 


3.94 


155 


3.18 


125 


2.29 


90 


1001 


-1250 


3.56 


140 


2.92 


115 


1.65 


65 


4.32 


170 


3.56 


140 


2.92 


115 


1251 


-1500 


3.56 


140 


2.92 


115 


2.03 


80 


4.32 


170 


3.56 


140 


2.92 


115 


1501 


-2000 


3.56 


140 


2.92 


115 


2.03 


80 


4.32 


170 


3.94 


155 


3.56 


140 



*Under a common overall covering such as a jacket, sheath, or armor. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-171 



310.110 



ARTICLE 310 — CONDUCTORS FOR GENERAL WIRING 



Table 310.104(E) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 to 35,000 Volts 



2001-5000 
Volts 



5001-8000 Volts 



8001-15,000 Volts 



15,001-25,000 Volts 



100 100 133 173 100 

Percent Percent Percent Percent Percent 

Conductor Insulation Insulation Insulation Insulation Insulation 

Size Level ' Level ' Level 2 Level 3 Level 1 

(AWG 

or kcniil) mm mils mm mils mm mils mm mils mm mils 



133 

Percent 

Insulation 

Level 2 



173 

Percent 

Insulation 

Level 3 



100 

Percent 

Insulation 

Level 1 



133 

Percent 

Insulation 

Level 2 



6-4 

2 

1 

1/0-2000 



2.29 
2.29 
2.29 
2.29 
2.29 



90 

90 
90 
90 

90 



2.92 
2.92 
2.92 
2.92 



115 
115 
115 
115 



3.56 
3.56 
3.56 
3.56 



140 
140 
140 
140 



4.45 
4.45 
4.45 
4.45 



175 
175 
175 
175 



4.45 
4.45 
4.45 



175 
175 
175 



5.59 
5.59 
5.59 



220 

220 
220 



6.60 260 
6.60 260 
6.60 260 



6.60 
6.60 



260 
260 



8.13 
8.13 



320 
320 



173 

Percent 

Insulation 

Level 3 



mils mm mils mm mils mm mils mm mils 



10.67 
10.67 



420 
420 



25,001-28,000 volts 



28,001-35,000 volts 



Conductor 

Size 
(AWG 



100 

Percent 

Insulation 

Level' 



133 

Percent 

Insulation 

Level 2 



173 

Percent 

Insulation 

Level 3 



100 

Percent 

Insulation 

Level 1 



133 

Percent 

Insulation 

Level 2 



173 

Percent 

Insulation 

Level 3 



or kcmil) 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils 


mm 


mils mm 


mils 


1 
1/0-2000 


7.11 
7.11 


280 

280 


8.76 
8.76 


345 
345 


11. .30 
11.30 


445 
445 


8.76 


345 


10.67 


420 14.73 


580 



100 Percent Insulation Level. Cables in this category shall be permitted to be applied where the system is provided with relay protection such 
that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. While these cables are applicable to the great majority 
of cable installations that are on grounded systems, they shall be permitted to be used also on other systems for which the application of cables is 
acceptable, provided the above clearing requirements are met in completely de-energizing the faulted section. 

133 Percent Insulation Level. This insulation level corresponds to that formerly designated for ungrounded systems. Cables in this category shall 
be permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and yet there is 
adequate assurance that the faulted section will be de-energized in a time not exceeding 1 hour. Also, they shall be permitted to be used in 
100 percent insulation level applications where additional insulation is desirable. 
3 173 Percent Insulation Level. Cables in this category shall be permitted to be applied under all of the following conditions: 

(1) In industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation 

(2) Where the fault clearing time requirements of the 1 33 percent level category cannot be met 

(3) Where an orderly shutdown is essential to protect equipment and personnel 

(4) There is adequate assurance that the faulted section will be de-energized in an orderly shutdown 

Also, cables with this insulation thickness shall be permitted to be used in 100 or 133 percent insulation level applications where additional 
insulation strength is desirable. 



Table 310.106(A) Minimum Size of Conductors 



Conductor 
Voltage Rating 

(Volts) 



0-2000 

2001-5000 

5001-8000 

8001-15.000 

15,001-28,000 

28,001-35,000 



Minimum Conductor Size (AWG) 

Aluminum or Copper-Clad 
Copper Aluminum 



14 
8 
6 
2 
1 

1/0 



12 
8 
6 
2 
1 

1/0 



(C) Stranded Conductors. Where installed in raceways, 
conductors 8 AWG and larger, not specifkali) permitted tn 
required elsewhere in this Code to be solid, shall be 
stranded. 



(D) Insulated. Conductors, not specifically permitted else- 
whi re in this Code to be covered or bare, shall be insulated. 

Informational Note: See 250.184 for insulation of neutral 
conductors of a solidly grounded high-voltage system. 

310.110 Conductor Identification. 

(A) Grounded Conductors. Insulated or covered grounded 
conductors shall be identified in accordance with 200.6. 

(B) Equipment Grounding Conductors. Equipment 
grounding conductors shall be in accordance with 250.119. 

(C) Ungrounded Conductors. Conductors that are in- 
tended for use as ungrounded conductors, whether used as a 
single conductor or in multiconductor cables, shall be fin- 
ished to be clearly distinguishable from grounded and 



70-172 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



312.1 



grounding conductors. Distinguishing markings shall not 
conflict in any manner with the surface markings required 
by 310.120(B)(1). Branch-circuit ungrounded conductors 
shall be identified in accordance with 210.5(C). Feeders 
shall be identified in accordance with 215.12. 

Exception: Conductor identification shall be permitted in 
accordance with 200.7. 

310.120 Marking. 

(A) Required Information. All conductors and cables 
shall be marked to indicate the following information, us- 
ing the applicable method described in 3 10. 120(B): 

(1) The maximum rated voltage. 

(2) The proper type letter or letters for the type of wire or 
cable as specified elsewhere in this Code. 

(3) The manufacturer's name, trademark, or other distinc- 
tive marking by which the organization responsible for 
the product can be readily identified. 

(4) The AWG size or circular mil area. 

Informational Note: See Conductor Properties, Table 8 of 
Chapter 9, for conductor area expressed in SI units for 
conductor sizes specified in AWG or circular mil area. 

(5) Cable assemblies where the neutral conductor is smaller 
than the ungrounded conductors shall be so marked. 

(B) Method of Marking. 

(1) Surface Marking. The following conductors and 
cables shall be durably marked on the surface. The AWG 
size or circular mil area shall be repeated at intervals not 
exceeding 610 mm (24 in.). All other markings shall be 
repeated at intervals not exceeding 1.0 m (40 in.). 

(1) Single-conductor and multiconductor rubber- and 
thermoplastic-insulated wire and cable 

(2) Nonmetallic-sheathed cable 

(3) Service-entrance cable 

(4) Underground feeder and branch-circuit cable 

(5) Tray cable 

(6) Irrigation cable 

(7) Power-limited tray cable 

(8) Instrumentation tray cable 

(2) Marker Tape. Metal-covered multiconductor cables 
shall employ a marker tape located within the cable and 
running for its complete length. 

L'.\ccptinii Ac. /: Tvpc Ml cable. 

Exception No. 2: Type AC cable. 

Exception No. 3: The information required in 31 0.120(A) 
shall be permitted to be durably marked on the outer non- 
metallic covering of Type MC, Type ITC, or Type PLTC 
cables at intervals not exceeding 1.0 m (40 in.). 



Exception No. 4: The information required in 310.120(A) 
shall be permitted to be durably marked on a nonmetallic 
covering under the metallic sheath of Type ITC or Type 
PLTC cable at intervals not exceeding 1.0 m (40 in.). 

Informational Note: Included in the group of metal- 
covered cables are Type AC cable (Article 320) , Type MC 
cable (Article 330), and lead sheathed cable. 

(3) Tag Marking. The following conductors and cables 
shall be marked by means of a printed tag attached to the 
coil, reel, or carton: 

(1) Type Ml cable 

(2) Switchboard wires 

(3) Metal-covered, single-conductor cables 

(4) Type AC cable 

(4) Optional Marking of Wire Size. The information re- 
quired in 3 10.1 20(A)(4) shall be permitted to be marked on 
the surface of the individual insulated conductors for the 
following multiconductor cables: 

(1) Type MC cable 

(2) Tray cable 

(3) Irrigation cable 

(4) Power-limited tray cable 

(5) Power-limited fire alarm cable 

(6) Instrumentation tray cable 

(C) Suffixes to Designate Number of Conductors. A type 
letter or letters used alone shall indicate a single insulated 
conductor. The letter suffixes shall be indicated as follows: 

(1) D — For two insulated conductors laid parallel within 
an outer nonmetallic covering 

(2) M — For an assembly of two or more insulated conduc- 
tors twisted spirally within an outer nonmetallic covering 

(D) Optional Markings. All conductors and cables con- 
tained in Chapter 3 shall be permitted to be surface marked 
to indicate special characteristics of the cable materials. 
These markings include, but are not limited to, markings 
for limited smoke, sunlight resistant, and so forth. 



ARTICLK 312 

Cabinets, Cutoul Boxes, and Meter 

Socket Enclosures 



312.1 Scope. This article covers the installation and con- 
struction specifications of cabinets, cutout boxes, and meter 
socket enclosures. 



201 1 Edition NATIONAL ELECTRICAL CODE 



70-173 



312.2 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



I. Installation 

312.2 Damp and Wet Locations. In damp or wet loca- 
tions, surface-type enclosures within the scope of this ar- 
ticle shall be placed or equipped so as to prevent moisture 
or water from entering and accumulating within the cabinet 
or cutout box, and shall be mounted so there is at least 
6-mm (Vi-in.) airspace between the enclosure and the wall 
or other supporting surface. Enclosures installed in wet lo- 
cations shall be weatherproof. For enclosures in wet loca- 
tions, raceways or cables entering above the level of unin- 
sulated live parts shall use fittings listed for wet locations. 

Exception: Nonmetallic enclosures shall be permitted to 
be installed without the airspace on a concrete, masonry, 
tile, or similar surface. 



Informational Note: 
300.6. 



For protection against corrosion, see 



312.3 Position in Wall. In walls of concrete, tile, or other 
noncombustible material, cabinets shall be installed so that 
the front edge of the cabinet is not set back of the finished 
surface more than 6 mm ('A in.). In walls constructed of 
wood or other combustible material, cabinets shall be flush 
with the finished surface or project therefrom. 

312.4 Repairing Noncombustible Surfaces. Noncombus- 
tible surfaces that are broken or incomplete shall be re- 
paired so there will be no gaps or open spaces greater than 
3 mm (Vs in.) at the edge of the cabinet or cutout box 
employing a flush-type cover. 

312.5 Cabinets, Cutout Boxes, and Meter Socket Enclo- 
sures. Conductors entering enclosures within the scope of 
this article shall be protected from abrasion and shall com- 
ply with 312.5(A) through (C). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 

(B) Metal Cabinets, Cutout Boxes, and Meter Socket 
Enclosures. Where metal enclosures within the scope of 
this article are installed with messenger-supported wiring, 
open wiring on insulators, or concealed knob-and-tube wir- 
ing, conductors shall enter through insulating bushings or, 
in dry locations, through flexible tubing extending from the 
last insulating support and firmly secured to the enclosure. 

(C) Cables. Where cable is used, each cable shall be se- 
cured to the cabinet, cutout box, or meter socket enclosure. 

Exception: Cables with entirely nonmetallic sheaths shall 
be permitted to enter the top of a surface-mounted enclo- 
sure through one or more nonflexible raceways not less 
than 450 mm (18 in.) and not more than 3.0 m (10 ft) in 
length, provided all of the following conditions are met: 



(a) Each cable is fastened within 300 mm (12 in.), 
measured along the sheath, of the outer end of the raceway. 

(b) The raceway extends directly above the enclosure 
and does not penetrate a structural ceiling. 

(c) A fitting is provided on each end of the raceway to 
protect the cable(s) from abrasion and the fittings remain 
accessible after installation. 

(d) The raceway is sealed or plugged, at the outer end 
using approved means so as to prevent access to the enclo- 
sure through the raceway. 

(e) The cable sheath is continuous through the race- 
way and extends into the enclosure beyond the fitting not 
less than 6 mm ('U in.). 

(f) The raceway is fastened at its outer end and at 
other points in accordance with the applicable article. 

(g) Where installed as conduit or tubing, the allowable 
cable fill does not exceed that permitted for complete con- 
duit or tubing systems by Table 1 of Chapter 9 of this Code 
and all applicable notes thereto. 

Informational Note: See Table 1 in Chapter 9, including 
Note 9, for allowable cable fill in circular raceways. See 
310.15(B)(3)(a) for required ampacity reductions for mul- 
tiple cables installed in a common raceway. 

312.6 Deflection of Conductors. Conductors at terminals 
or conductors entering or leaving cabinets or cutout boxes 
and the like shall comply with 312.6(A) through (C). 

Exception: Wire-bending space in enclosures for motor 
controllers with provisions for one or two wires per termi- 
nal shall comply with 430.10(B). 

(A) Width of Wiring Gutters. Conductors shall not be de- 
flected within a cabinet or cutout box unless a gutter having a 
width in accordance with Table 312.6(A) is provided. Conduc- 
tors in parallel in accordance with 310.10(H) shall be judged 
on the basis of the number of conductors in parallel. 

(B) Wire-Bending Space at Terminals. Wire-bending space 
at each terminal shall be provided in accordance with 
312.6(B)(1) or (B)(2). 

(1) Conductors Not Entering or Leaving Opposite Wall. 

Table 312.6(A) shall apply where the conductor does not 
enter or leave the enclosure through the wall opposite its 
terminal. 

(2) Conductors Entering or Leaving Opposite Wall. Table 
312.6(B) shall apply where the conductor does enter or 
leave the enclosure through the wall opposite its terminal. 

Exception No. 1: Where the distance between the wall and 
its terminal is in accordance with Table 312.6(A), a con- 
ductor shall be permitted to enter or leave an enclosure 



70-174 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 312 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



312.10 



Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters 















Wires per 


Terminal 














1 




2 






3 




4 




5 




Wire Size (AWG or 


















































kcmil) 


mm 




in. 


mm 


in. 


mm 




in. 


mm 


in. 


mm 


in. 


14-10 


Not 


specified 




























8-6 


38.1 




l'/2 


— 


— 


— 




— 


— 


— 


— 


— 


4-3 


50.8 




2 


— 


— 


— 




— 


— 


— 


— 


— 


2 


63.5 




2'/2 


— 


— 


— 




— 


— 


— 


— 


— 


1 


76.2 




3 


— 


— 


— 




— 


— 


— 


— 


— 


1/0-2/0 


88.9 




Vh 


127 


5 


178 




7 











* 


3/0-4/0 


102 




4 


152 


6 


203 




8 


— 


— 


— 


— 


250 


114 




4'/2 


152 


6 


203 




8 


254 


10 


— 


— 


300-350 


127 




5 


203 


8 


254 




10 


305 


12 


— 


— 


400-500 


152 




6 


203 


8 


254 




10 


305 


12 


356 


14 


600-700 


203 




8 


254 


10 


305 




12 


356 


14 


406 


16 


750-900 


203 




8 


305 


12 


356 




14 


406 


16 


457 


18 


1000-1250 


254 




10 


— 


— 


— 




— 


— 


— 


— 


— 


1500-2000 


305 




12 


— 


— 


— 




— 


— 


— 


— 


— 



Note: Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector (in the direction that the wire leaves 
the terminal) to the wall, barrier, or obstruction. 



through the wall opposite its terminal, provided the con- 
ductor enters or leaves the enclosure where the gutter joins 
an adjacent gutter that has a width that conforms to Table 
312.6(B) for the conductor. 

Exception No. 2: A conductor not larger than 350 kcmil 
shall be permitted to enter or leave an enclosure containing 
only a meter socket(s) through the wall opposite its termi- 
nal, provided the distance between the terminal and the 
opposite wall is not less than that specified in Table 
312.6(A) and the terminal is a lay-in type, where the termi- 
nal is either of the following: 

(a) Directed toward, the opening in the enclosure and 
within a 45 degree angle of directly facing the enclosure 
wall 

(b) Directly facing the enclosure wall and offset not 
greater than 50 percent of the bending space specified in 
Table 312.6(A) 

Informational Note: Offset is the distance measured along 
the enclosure wall from the axis of the centerline of the 
terminal to a line passing through the center of the opening 
in the enclosure. 

(C) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(G). 

312.7 Space in Enclosures. Cabinets and cutout boxes 
shall have sufficient space to accommodate all conductors 
installed in them without crowding. 

312.8 Switch and Overcurrent Device i nclosures with 
Spikes. Tsips, mid Feed-Through Conductors. The wil- 



ing space ol enclq tire foi sw tches ot bvercurreht d< vices 
shall be p« emitted for conductors feeding through, spliced, 
or tapping oil" io other enclosures, switches, oi ovi rcurrent 
devices where all of the following con blionj .ire met: 

(1) The total of all conductors installed at any era; s section 
i.J i!. v wi, >hl' -.pa.'s does no> exceed 10 percent or the 
cross-sectional area of thai space. 

(2) Ths total area oi all conductors, splices, and taps in- 
stalled ai am cross section oi the wiring space does not 
exceed 75 percent of th< cro : sectional area of that 
space. 

(3) A warning label is applied U< the enclosure that identi- 
fies the closes! disconnecting means fv any feed- 
Ihro ijih conductors. 

312.9 Side or Back Wiring Spaces or Gutters. Cabinets 
and cutout boxes shall be provided with back-wiring 
spaces, gutters, or wiring compartments as required by 
312.11(C) and (D). 



II. Construction Specifications 

312.10 Material. Cabinets, cutout boxes, and meter socket 
enclosures shall comply with 312.10(A) through (C). 

(A) Metal Cabinets and Cutout Boxes. Metal enclosures 
within the scope of this article shall be protected both in- 
side and outside against corrosion. 

Informational Note: For information on protection against 
corrosion, see 300.6. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-175 



312.11 



ARTICLE 3 12 — CABINETS, CUTOUT BOXES, AND METER SOCKET ENCLOSURES 



Table 312.6(B) Minimum Wire-Bending Space at Terminals 














Wires per Terminal 


Wire Size (AWG or kcmil) 


1 


2 


3 


4 or 


More 




Compact 


















Stranded 


















AA-8000 


















Aluminum 


















Alloy 
















All Other 


Conductors 
















Conductors 


(See Note 3.) 


mm in. 


mm 


in. 


mm 


in. 


mm 


in. 


14-10 


12-8 


Not specified 













— 


— 


8 


6 


38.1 l'/2 


— 


— 


— 




— 


— 


6 


4 


50.8 2 


— 


— 


— 




— 


— 


4 


2 


76.2 3 


— 


— 


— 




— 


— 


3 


1 


76.2 3 


— 


— 


— 




— 


— 


2 


1/0 


88.9 3'/2 


— 


— 


— 




— 


— 


1 


2/0 


114 4'/2 


— 


— 


— 




— 


— 


1/0 


3/0 


140 5'/2 


140 


5'/2 


178 


7 





— 


2/0 


4/0 


152 6 


152 


6 


190 


7!/2 


— 


— 


3/0 


250 


165 a 6'/2 a 


165 a 


6'/2 a 


203 


8 


— 


— 


4/0 


300 


178 b 7 b 


190" 


7'/2 C 


216 a 


8'/2" 


— 


— 


250 


350 


216" 8'/2 d 


229 d 


8'/2 d 


254 b 


9 b 


254 


10 


300 


400 


254" 10" 


254 d 


10 d 


279 b 


11" 


305 


12 


350 


500 


305" 12" 


305" 


12" 


330" 


13" 


356 d 


14 d 


400 


600 


330" 13" 


330" 


13" 


356" 


14" 


381" 


15" 


500 


700-750 


356" 14" 


356" 


14" 


381" 


15" 


406" 


16" 


600 


800-900 


381" 15" 


406" 


16" 


457" 


18" 


483" 


19" 


700 


1000 


406" 16" 


457" 


18" 


508" 


20" 


559" 


22" 


750 


— 


432" 17" 


483" 


19" 


559" 


22" 


610" 


24" 


800 





457 18 


508 


20 


559 


22 


610 


24 


900 


— 


483 19 


559 


22 


610 


24 


610 


24 


1000 


— 


508 20 


— 


— 


— 




— 




1250 


— 


559 22 


— 


— 


— 




— 




1500 


— 


610 24 


— 


— 


— 




— 




1750 


— 


610 24 


— 


— 


— 




— 




2000 


— 


610 24 


— 


— 


— 




— 





1. Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector in a direction perpendicular to the 
enclosure wall. 

2. For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to be reduced by the following number 
of millimeters (inches): 

a 12.7 mm {Vi in.) 
b 25.4 mm (1 in.) 
" 38.1 mm (l'/2 in.) 
d 50.8 mm (2 in.) 
' 76.2 mm (3 in.) 

3. This column shall be permitted to determine the required wire-bending space for compact stranded aluminum conductors in sizes up to 1000 
kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material in accordance with 310.14. 



(B) Strength. The design and construction of enclosures 
within the scope of this article shall be such as to secure ample 
strength and rigidity. If constructed of sheet steel, the metal 
thickness shall not be less than 1 .35 mm (0.053 in.) uncoated. 

(C) Nonmetallic Cabinets. Nonmetallic cabinets shall be 
listed, or they shall be submitted for approval prior to in- 
stallation. 



312.11 Spacing. The spacing within cabinets and cutout 
boxes shall comply with 312.11(A) through (D). 

(A) General. Spacing within cabinets and cutout boxes 
shall be sufficient to provide ample room for the distribu- 
tion of wires and cables placed in them and for a separation 
between metal parts of devices and apparatus mounted 
within them in accordance with (A)(1), (A)(2), and (A)(3). 



70-176 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 3 14 -OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES ;FITTINGS; AND HANDBOLES 314.15 



(1) Base. Other than at points of support, there shall be an 
airspace of at least 1.59 mm (0.0625 in.) between the base 
of the device and the wall of any metal cabinet or cutout 
box in which the device is mounted. 

(2) Doors. There shall be an airspace of at least 25.4 mm 
(1.00 in.) between any live metal part, including live metal 
parts of enclosed fuses, and the door. 

Exception: Where the door is lined with an approved in- 
sulating material or is of a thickness of metal not less than 
2.36 mm (0.093 in.) uncoated, the airspace shall not be less 
than 12.7 mm (0.500 in.). 

(3) Live Parts. There shall be an airspace of at least 
12.7 mm (0.500 in.) between the walls, back, gutter parti- 
tion, if of metal, or door of any cabinet or cutout box and 
the nearest exposed current-carrying part of devices 
mounted within the cabinet where the voltage does not 
exceed 250. This spacing shall be increased to at least 
25.4 mm (1.00 in.) for voltages of 251 to 600, nominal. 

Exception: Where the conditions in 312.11(A)(2), Excep- 
tion, are met, the airspace for nominal voltages from 251 to 
600 shall be permitted to be not less than 12.7 mm 
(0.500 in.). 

(B) Switch Clearance. Cabinets and cutout boxes shall be 
deep enough to allow the closing of the doors when 30- 
ampere branch-circuit panelboard switches are in any posi- 
tion, when combination cutout switches are in any position, 
or when other single-throw switches are opened as far as 
their construction permits. 

(C) Wiring Space. Cabinets and cutout boxes that contain 
devices or apparatus connected within the cabinet or box to 
more than eight conductors, including those of branch cir- 
cuits, meter loops, feeder circuits, power circuits, and simi- 
lar circuits, but not including the supply circuit or a continua- 
tion thereof, shall have back-wiring spaces or one or more 
side- wiring spaces, side gutters, or wiring compartments. 

(D) Wiring Space — Enclosure. Side-wiring spaces, side 
gutters, or side-wiring compartments of cabinets and cutout 
boxes shall be made tight enclosures by means of covers, 
barriers, or partitions extending from the bases of the de- 
vices contained in the cabinet, to the door, frame, or sides 
of the cabinet. 

Exception: Side-wiring spaces, side gutters, and side-wiring 
compartments of cabinets shall not be required to be made 
tight enclosures where those side spaces contain only conduc- 
tors that enter the cabinet directly opposite to the devices 
where they terminate. 

Partially enclosed back-wiring spaces shall be provided 
with covers to complete the enclosure. Wiring spaces that 
are required by 312.11(C) and are exposed when doors are 



open shall be provided with covers to complete the enclo- 
sure. Where adequate space is provided for feed-through 
conductors and for splices as required in 312.8, additional 
barriers shall not be required. 



ARTICLE 3J4 
Outlet. Device, Pull, and Junction Boxes; 
Conduit Bodies: Fittings; and Handhole 

■ 'Enclosures' 



I. Scope and General 

314.1 Scope. This article covers the installation and use of 
all boxes and conduit bodies used as outlet, device, junc- 
tion, or pull boxes, depending on their use, and handhole 
enclosures. Cast, sheet metal, nonmetallic, and other boxes 
such as FS, FD, and larger boxes are not classified as con- 
duit bodies. This article also includes installation require- 
ments for fittings used to join raceways and to connect 
raceways and cables to boxes and conduit bodies. 

314.2 Round Boxes. Round boxes shall not be used where 
conduits or connectors requiring the use of locknuts or 
bushings are to be connected to the side of the box. 

314.3 Nonmetallic Boxes. Nonmetallic boxes shall be per- 
mitted only with open wiring on insulators, concealed knob- 
and-tube wiring, cabled wiring methods with entirely nonme- 
tallic sheaths, flexible cords, and nonmetallic raceways. 

Exception No. 1: Where internal bonding means are pro- 
vided between all entries, nonmetallic boxes shall be per- 
mitted to be used with metal raceways or metal-armored 
cables. 

Exception No. 2: Where integral bonding means with a 
provision for attaching an equipment bonding jumper in- 
side the box are provided between all threaded entries in 
nonmetallic boxes listed for the purpose, nonmetallic boxes 
shall be permitted to be used with metal raceways or metal- 
armored cables. 

314.4 Metal Boxes. Metal boxes shall be grounded and 
bonded in accordance with Parts I, IV, V, VI, VII, and X of 
Article 250 as applicable, except as permitted in 250.112(1). 

II. Installation 

314.15 Damp or Wet Locations. In damp or wet loca- 
tions, boxes, conduit bodies, and fittings shall be placed or 
equipped so as to prevent moisture from entering or accu- 
mulating within the box, conduit body, or fitting. Boxes, 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-177 



314.16 ARTICLE 3 1 4 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 



conduit bodies, and fittings installed in wet locations shall 
be listed for use in wet locations. 

Informational Note No. 1: For boxes in floors, see 
314.27(B). 

Informational Note No. 2: For protection against corro- 
sion, see 300.6. 

314.16 Number of Conductors in Outlet, Device, and 
Junction Boxes, and Conduit Bodies. Boxes and conduit 
bodies shall be of sufficient size to provide free space for 
all enclosed conductors. In no case shall the volume of the 
box, as calculated in 314.16(A), be less than the fill calcu- 
lation as calculated in 314.16(B). The minimum volume for 
conduit bodies shall be as calculated in 314.16(C). 

The provisions of this section shall not apply to termi- 
nal housings supplied with motors or generators. 

Informational Note: For volume requirements of motor or 
generator terminal housings, see 430.12. 

Boxes and conduit bodies enclosing conductors 4 AWG 
or larger shall also comply with the provisions of 314.28. 

(A) Box Volume Calculations. The volume of a wiring 
enclosure (box) shall be the total volume of the assembled 
sections and, where used, the space provided by plaster 
rings, domed covers, extension rings, and so forth, that are 
marked with their volume or are made from boxes the di- 
mensions of which are listed in Table 314.16(A). 

(1) Standard Boxes. The volumes of standard boxes that 
are not marked with their volume shall be as given in Table 
314.16(A). 

(2) Other Boxes. Boxes 1650 cm 3 (100 in. 3 ) or less, other 
than those described in Table 314.16(A), and nonmetallic 
boxes shall be durably and legibly marked by the manufac- 
turer with their volume. Boxes described in Table 314.16(A) 
that have a volume larger than is designated in the table 
shall be permitted to have their volume marked as required 
by this section. 

(B) Box Fill Calculations. The volumes in paragraphs 
314.16(B)(1) through (B)(5), as applicable, shall be added 
together. No allowance shall be required for small fittings 
such as locknuts and bushings. 

(1) Conductor Fill. Each conductor that originates outside 
the box and terminates or is spliced within the box shall be 
counted once, and each conductor that passes through the 
box without splice or termination shall be counted once. 
Each loop or coil of unbroken conductor not less than twice 
the minimum length required for free conductors in 300.14 
shall be counted twice. The conductor fill shall be calcu- 
lated using Table 314.16(B). A conductor, no part of which 
leaves the box, shall not be counted. 



Exception: An equipment grounding conductor or conduc- 
tors or not over four fixture wires smaller than 14 AWG, or 
both, shall be permitted to be omitted from the calculations 
where they enter a box from a domed luminaire or similar 
canopy and terminate within that box. 

(2) Clamp Fill. Where one or more internal cable clamps, 
whether factory or field supplied, are present in the box, a 
single volume allowance in accordance with Table 314.16(B) 
shall be made based on the largest conductor present in the 
box. No allowance shall be required for a cable connector with 
its clamping mechanism outside the box. 

(3) Support Fittings Fill. Where one or more luminaire 
studs or hickeys are present in the box, a single volume 
allowance in accordance with Table 314.16(B) shall be 
made for each type of fitting based on the largest conductor 
present in the box. 

(4) Device or Equipment Fill. For each yoke or strap con- 
taining one or more devices or equipment, a double volume 
allowance in accordance with Table 314.16(B) shall be 
made for each yoke or strap based on the largest conductor 
connected to a device(s) or equipment supported by that 
yoke or strap. A device or utilization equipment wider than 
a single 50 mm (2 in.) device box as described in Table 
314.16(A) shall have double volume allowances provided 
for each gang required for mounting. 

(5) Equipment Grounding Conductor Fill. Where one or 
more equipment grounding conductors or equipment bonding 
jumpers enter a box, a single volume allowance in accordance 
with Table 314.16(B) shall be made based on the largest 
equipment grounding conductor or equipment bonding jumper 
present in the box. Where an additional set of equipment 
grounding conductors, as permitted by 250.146(D), is present 
in the box, an additional volume allowance shall be made 
based on the largest equipment grounding conductor in the 
additional set. 

(C) Conduit Bodies. 

(1) General. Conduit bodies enclosing 6 AWG conductors 
or smaller, other than short-radius conduit bodies as de- 
scribed in 314.16(C)(2), shall have a cross-sectional area 
not less than twice the cross-sectional area of the largest 
conduit or tubing to which they can be attached. The maxi- 
mum number of conductors permitted shall be the maxi- 
mum number permitted by Table 1 of Chapter 9 for the 
conduit or tubing to which it is attached. 

(2) With Splices, Taps, or Devices. Only those conduit 
bodies that are durably and legibly marked by the manufac- 
turer with their volume shall be permitted to contain 
splices, taps, or devices. The maximum number of conduc- 
tors shall be calculated in accordance with 314.16(B). Con- 
duit bodies shall be supported in a rigid and secure manner. 



70-178 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT B0DIES;F1TT1NGS; AND HANDBOLES 314.17 



Table 314.16(A) 


Metal Boxes 






















Box Trade Size 


Minimum 
Volume 




Maximum Number of Conductors* 
(arranged by AWG size) 




mm 


in. 




cm 3 


in. 3 


18 


16 


14 


12 


10 


8 


6 


100 x 32 
100 x 38 
100 x 54 


(4x VA) 
(4 x 1 Vi) 

(4 x VA) 


round/octagonal 
round/octagonal 
round/octagonal 


205 

254 
353 


12.5 
15.5 
21.5 


8 

10 
14 


7 

8 

12 


6 

7 

10 


5 
6 
9 


5 
6 
8 


5 
5 
7 


2 
3 
4 


100 x 32 
100 x 38 
100 x 54 


(4x 1 1/4) 
(4 x 1 Vi) 
(4 x VA) 


square 
square 
square 


295 

344 
497 


18.0 
21.0 
30.3 


12 
14 
20 


10 
12 
17 


9 
10 

15 


8 
9 

13 


7 
8 
12 


6 

7 
10 


3 
4 
6 


120 x 32 
120 x 38 
120 x 54 


(4"/i6X VA) 
(4"/iex VA) 
(4"/i<s x VA) 


square 
square 
square 


418 
484 
689 


25.5 
29.5 
42.0 


17 
19 

28 


14 
16 
24 


12 
14 
21 


11 

13 
18 


10 
11 
16 


8 
9 

14 


5 
5 

8 


75 x 50 x 38 
75 x 50 x 50 
75x 50 x 57 
75 x 50 x 65 
75 x 50 x 70 
75 x 50 x 90 


(3x2x1 Vi) 
(3x2x2) 
(3x 2 x VA) 
(3 x 2 x VA) 
(3 x 2 x 2 3 /i) 
(3 x 2 x VA) 


device 
device 
device 
device 
device 
device 


123 
164 
172 
205 
230 
295 


7.5 
10.0 
10.5 
12.5 
14.0 
18.0 


5 
6 
7 
8 
9 
12 


4 
5 
6 
7 
8 
10 


3 
5 
5 
6 

7 
9 


3 
4 

4 
5 
6 
8 


3 
4 

4 
5 
5 
7 


2 
3 
3 
4 
4 
6 


1 

2 
2 
2 
2 
3 


100 x 54 x 38 
100 x 54 x 48 
100 x 54 x 54 


(4x2'/ 8 x VA) 
(4 x 2'/s x VA) 
(4 x 2'/s x VA) 


device 
device 
device 


169 

213 
238 


10.3 
13.0 
14.5 


6 
8 
9 


5 
7 
8 


5 
6 

7 


4 
5 
6 


4 
5 
5 


3 
4 

4 


2 
2 
2 


95 x 50 x 65 
95 x 50 x 90 


{VA x 2 x 2'/ 2 ) 
(3% x 2 x 3'/ 2 ) 


masonry box/gang 
masonry box/gang 


230 
344 


14.0 
21.0 


9 

14 


8 
12 


7 
10 


6 
9 


5 
8 


4 
7 


2 
4 


min. 44.5 depth 
min. 60.3 depth 


FS — single cover/gang (l-Vi) 
FD — single cover/gang (2 3 /s) 


221 
295 


13.5 
18.0 


9 
12 


7 
10 


6 
9 


6 
8 


5 

7 


4 
6 


2 
3 


min. 44.5 depth 
min. 60.3 depth 


FS — multiple cover/gang (P/4) 
FD — multiple cover/gang (2 3 /s) 


295 
395 


18.0 
24.0 


12 
16 


10 
13 


9 
12 


8 
10 


7 
9 


6 

8 


3 

4 



*Where no volume allowances are required by 314.16(B)(2) through (B)(5). 



Table 314.16(B) Volume Allowance Required per Conductor 





Free Space 


Within Box for Each 


Size of Conductor 




Conductor 










(AWG) 


cm 3 




in. 3 


18 


24.6 




1.50 


16 


28.7 




1.75 


14 


32.8 




2.00 


12 


36.9 




2.25 


10 


41.0 




2.50 


8 


49.2 




3.00 


6 


81.9 




5.00 



(3) Short Radius Conduit Bodies. Conduit bodies such as 

capped elbows mid service-entrance elbows l'mc enclose 
conductors 6 AWG or Mnalltr. and are onl. intended to 
enable the installation ; >1 the raceway and the contained 
conductors, sht'l not comaist .,|<liec., r.ip-, iv devices and 



shall bi of sufficient size to provide fret space for all con- 
ductors enclosed in the conduit body. 

314.17 Conductors Entering Boxes, Conduit Bodies, or 
Fittings. Conductors entering boxes, conduit bodies, or fit- 
tings shall be protected from abrasion and shall comply 
with 314.17(A) through (D). 

(A) Openings to Be Closed. Openings through which con- 
ductors enter shall be adequately closed. 

(B) Metal Boxes and Conduit Bodies. Where metal boxes 
or conduit bodies are installed with messenger-supported 
wiring, open wiring on insulators, or concealed knob-and- 
tube wiring, conductors shall enter through insulating bush- 
ings or, in dry locations, through flexible tubing extending 
from the last insulating support to not less than 6 mm 
0/4 in.) inside the box and beyond any cable clamps. Except 
as provided in 300.15(C), the wiring shall be firmly secured 
to the box or conduit body. Where raceway or cable is 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-179 



314.19 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 



installed with metal boxes or conduit bodies, the raceway 
or cable shall be secured to such boxes and conduit bodies. 

(C) Nonmetallic Boxes and Conduit Bodies. Nonmetallic 
boxes and conduit bodies shall be suitable for the lowest 
temperature-rated conductor entering the box. Where non- 
metallic boxes and conduit bodies are used with messenger- 
supported wiring, open wiring on insulators, or concealed 
knob-and-tube wiring, the conductors shall enter the box 
through individual holes. Where flexible tubing is used to 
enclose the conductors, the tubing shall extend from the last 
insulating support to not less than 6 mm ('A in.) inside the 
box and beyond any cable clamp. Where nonmetallic- 
sheathed cable or multiconductor Type UF cable is used, 
the sheath shall extend not less than 6 mm ('A in.) inside 
the box and beyond any cable clamp. In all instances, all 
permitted wiring methods shall be secured to the boxes. 

Exception: Where nonmetallic- sheathed cable or multi- 
conductor Type UF cable is used with single gang boxes 
not larger than a nominal size 57 mm x 100 mm (2'A in. 
x 4 in.) mounted in walls or ceilings, and where the cable 
is fastened within 200 mm (8 in.) of the box measured along 
the sheath and where the sheath extends through a cable 
knockout not less than 6 mm ('A in.), securing the cable to 
the box shall not be required. Multiple cable entries shall 
be permitted in a single cable knockout opening. 

(D) Conductors 4 AWG or Larger. Installation shall com- 
ply with 300.4(G). 

Informational Note: See 110.12(A) for requirements on 
closing unused cable and raceway knockout openings. 

314.19 Boxes Enclosing Flush Devices. Boxes used to en- 
close flush devices shall be of such design that the devices 
will be completely enclosed on back and sides and substan- 
tial support for the devices will be provided. Screws for 
supporting the box shall not be used in attachment of the 
device contained therein. 

314.20 In Wall or Ceiling. In walls or ceilings with a 
surface of concrete, tile, gypsum, plaster, or other noncom- 
bustible material, boxes employing a flush-type cover or 
faceplate shall be installed so that the front edge of the box, 
plaster ring, extension ring, or listed extender will not be 
set back of the finished surface more than 6 mm ('/i in.). 

In walls and ceilings constructed of wood or other com- 
bustible surface material, boxes, plaster rings, extension 
rings, or listed extenders shall be flush with the finished 
surface or project therefrom. 

314.21 Repairing Noncombustihlc Surfaces. Noncombus- 
tible surfaces that are broken or incomplete around boxes 
employing a flush-type cover or faceplate shall be repaired 



so there will be no gaps or open spaces greater than 3 mm 
('/s in.) at the edge of the box. 

314.22 Surface Extensions. Surface extensions shall be 
made by mounting and mechanically securing an extension 
ring over the box. Equipment grounding shall be in accor- 
dance with Part VI of Article 250. 

Exception: A surface extension shall be permitted to be 
made from the cover of a box where the cover is designed 
so it is unlikely to fall off or be removed if its securing 
means becomes loose. The wiring method shall be flexible 
for a length sufficient to permit removal of the cover and 
provide access to the box interior, and arranged so that any 
grounding continuity is independent of the connection be- 
tween the box and cover. 

314.23 Supports. Enclosures within the scope of this ar- 
ticle shall be supported in accordance with one or more of 
the provisions in 314.23(A) through (H). 

(A) Surface Mounting. An enclosure mounted on a build- 
ing or other surface shall be rigidly and securely fastened in 
place. If the surface does not provide rigid and secure sup- 
port, additional support in accordance with other provisions 
of this section shall be provided. 

(B) Structural Mounting. An enclosure supported from a 
structural member of a building or from grade shall be 
rigidly supported either directly or by using a metal, poly- 
meric, or wood brace. 

(1) Nails and Screws. Nails and screws, where used as a 
fastening means, shall be attached by using brackets on the 
outside of the enclosure, or they shall pass through the 
interior within 6 mm {'A in.) of the back or ends of the 
enclosure. Screws shall not be permitted to pass through the 
box unless exposed threads in the box are protected using 
approved means to avoid abrasion of conductor insulation. 

(2) Braces. Metal braces shall be protected against corro- 
sion and formed from metal that is not less than 0.51 mm 
(0.020 in.) thick uncoated. Wood braces shall have a cross 
section not less than nominal 25 mm x 50 mm (1 in. 
x 2 in.). Wood braces in wet locations shall be treated for 
the conditions. Polymeric braces shall be identified as being 
suitable for the use. 

(C) Mounting in Finished Surfaces. An enclosure mounted 
in a finished surface shall be rigidly secured thereto by clamps, 
anchors, or fittings identified for the application. 

(D) Suspended Ceilings. An enclosure mounted to struc- 
tural or supporting elements of a suspended ceiling shall be 
not more than 1650 cm 3 (100 in. 3 ) in size and shall be 
securely fastened in place in accordance with either (D)(1) 
or (D)(2). 



70-180 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 3 1 4 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 314.23 



(1) Framing Members. An enclosure shall be fastened to 
the framing members by mechanical means such as bolts, 
screws, or rivets, or by the use of clips or other securing 
means identified for use with the type of ceiling framing 
member(s) and enclosure(s) employed. The framing mem- 
bers shall be adequately supported and securely fastened to 
each other and to the building structure. 

(2) Support Wires. The installation shall comply with the 
provisions of 300.11(A). The enclosure shall be secured, using 
methods identified for the purpose, to ceiling support wfre(s), 
including any additional support wire(s) installed for that pur- 
pose. Support wire(s) used for enclosure support shall be fas- 
tened at each end so as to be taut within the ceiling cavity. 

(E) Raceway Supported Enclosure, Without Devices, 
Luminaires, or Lampholders. An enclosure that does not 
contain a device(s) other than splicing devices or support a 
luminaire(s), lampholder, or other equipment and is sup- 
ported by entering raceways shall not exceed 1650 cm 3 
(100 in. 3 ) in size. It shall have threaded entries or have 
hubs identified for the purpose. It shall be supported by two 
or more conduits threaded wrenchtight into the enclosure or 
hubs. Each conduit shall be secured within 900 mm (3 ft) of 
the enclosure, or within 450 mm (18 in.) of the enclosure if 
all conduit entries are on the same side. 

Except ion: The following wiring methods shall be permit- 
ted to support a conduit body of any size, including a con- 
duit body constructed with only one conduit entry, if the 
trade size of the conduit body is not larger than the largest 
trade size of the conduit or tubing: 

(!) intermediate metal conduit. Type IMC 

(2) Rigid metal conduit, Type RMC 

(3) Rigid polyvinyl chloride conduit. Type PVC 

(4) Reinforced thermosetting resin conduit. Type RTRC 

(5) Electrical metallic tubing, Type EMT 

(F) Raceway-Supported Enclosures, with Devices, Lu- 
minaires, or Lampholders. An enclosure that contains a 
device(s), other than splicing devices, or supports a lumi- 
nals), lampholder, or other equipment and is supported by 
entering raceways shall not exceed 1650 cm 3 (100 in. 3 ) in 
size. It shall have threaded entries or have hubs identified for 
the purpose. It shall be supported by two or more conduits 
threaded wrenchtight into the enclosure or hubs. Each conduit 
shall be secured within 450 mm (18 in.) of the enclosure. 

Exception No. 1: Rigid metal or intermediate metal con- 
duit shall be permitted to support a conduit body of any 
size, including a conduit body constructed with only one 
conduit entry, provided the trade size of the conduit body is 
not larger than the largest trade size of the conduit. 

Exception No. 2: An unbroken length(s) of rigid or inter- 
mediate metal conduit shall be permitted to support a box 



used for luminaire or lampholder support, or to support a 
wiring enclosure that is an integral part of a luminaire and 
used in lieu of a box in accordance with 300.15(B), where 
all of the following conditions are met: 

(a) The conduit is securely fastened at a point so that 
the length of conduit beyond the last point of conduit sup- 
port does not exceed 900 mm (3 ft). 

(b) The unbroken conduit length before the last point 
of conduit support is 300 mm (12 in.) or greater, and that 
portion of the conduit is securely fastened at some point not 
less than 300 mm (12 in.) from its last point of support. 

(c) Where accessible to unqualified persons, the lumi- 
naire or lampholder, measured to its lowest point, is at least 
2.5 m (8 ft) above grade or standing area and at least 
900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) 
elevation from windows, doors, porches, fire escapes, or 
similar locations. 

(d) A luminaire supported by a single conduit does not 
exceed 300 mm (12 in.) in any direction from the point of 
conduit entry. 

(e) The weight supported by any single conduit does 
not exceed 9 kg (20 lb). 

(f) At the luminaire or lampholder end, the conduit(s) 
is threaded wrenchtight into the box, conduit body, or inte- 
gral wiring enclosure, or into hubs identified for the pur- 
pose. Where a box or conduit body is used for support, the 
luminaire shall be secured directly to the box or conduit 
body, or through a threaded conduit nipple not over 75 mm 
(3 in.) long. 

(G) Enclosures in Concrete or Masonry. An enclosure 
supported by embedment shall be identified as suitably pro- 
tected from corrosion and securely embedded in concrete or 
masonry. 

(H) Pendant Boxes. An enclosure supported by a pendant 
shall comply with 314.23(H)(1) or (H)(2). 

(1) Flexible Cord. A box shall be supported from a mul- 
ticonductor cord or cable in an approved manner that pro- 
tects the conductors against strain, such as a strain-relief 
connector threaded into a box with a hub. 

(2) Conduit. A box supporting lampholders or luminaires, 
or wiring enclosures within luminaires used in lieu of boxes 
in accordance with 300.15(B), shall be supported by rigid 
or intermediate metal conduit stems. For stems longer than 
450 mm (18 in.), the stems shall be connected to the wiring 
system with flexible fittings suitable for the location. At the 
luminaire end, the conduit(s) shall be threaded wrenchtight 
into the box or wiring enclosure, or into hubs identified for 
the purpose. 

Where supported by only a single conduit, the threaded 
joints shall be prevented from loosening by the use of set- 
screws or other effective means, or the luminaire, at any 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-181 



314.24 ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 



point, shall be at least 2.5 ra (8 ft) above grade or standing 
area and at least 900 mm (3 ft) measured horizontally to the 
2.5 m (8 ft) elevation from windows, doors, porches, fire 
escapes, or similar locations. A luminaire supported by a 
single conduit shall not exceed 300 mm (12 in.) in any 
horizontal direction from the point of conduit entry. 

314.24 Depth of Boxes. Outlet and device boxes shall 
have sufficient depth to allow equipment installed within 
them to be mounted properly and without likelihood of 
damage to conductors within the box. 

(A) Outlet Boxes Without Enclosed Devices or Utiliza- 
tion Equipment. Outlet bo-<es that do noi enclose devices 
or utilization equipment shall have a Tnhiuiumi internal 
depth of 12.7 mm C/2 in.). 

(B) Outlet and Device Boxes with Enclosed Devices or 
Utilization Equipment. Outlet and device boxes that en- 
close devices or utilization equipment shall have a mini- 
mum internal depth that accommodates the rearward pro- 
jection of the equipment and the size of the conductors that 
supply the equipment. The internal depth shall include, 
where used, that of any extension boxes, plaster rings, or 
raised covers. The internal depth shall comply with all ap- 
plicable provisions of (B)(1) through (B)(5). 

(1) Large Equipment. Boxes that enclose devices or uti- 
lization equipment that projects more than 48 mm (1% in.) 
rearward from the mounting plane of the box shall have a 
depth that is not less than the depth of the equipment plus 
6 mm ((A in.). 

(2) Conductors Larger Than 4 AWG. Boxes that enclose 
tle\ ices or utilization equipment supplied by conductors 
larger than 4 AWG shall be identified for their specific 
function. 

Exception to (2): Devices or mill ation equipment supplied 
bye ndtictors large > than '1 \\Mt shall '• permitted to be 
mounted on or in junction and pull boxes target tha.i 
1650 cm (100 in:) if the spacing at the terminals meets 
the requirements of M2.(i. 

(3) Conductors 8, 6, or 4 AWG. Boxes that enclose de- 
vices or utilization equipment supplied by 8, 6, or 4 AWG 
conductors shall have an internal depth that is not less than 
52.4 mm (2'/i6 in.). 

(4) Conductors 12 or 10 AWG. Boxes that enclose de- 
vices or utilization equipment supplied by 12 or 10 AWG 
conductors shall have an internal depth that is not less than 
30.2 mm (P/i6 in.). Where the equipment projects rearward 
from the mounting plane of the box by more than 25 mm 
(1 in.), the box shall have a depth not less than that of the 
equipment plus 6 mm ( ] A in.). 



(5) Conductors 14 AWG and Smaller. Boxes that enclose 

devices < i utilization equipment supplied by 14 AWG or 
smaller conductors shall have a depth that is not less than 
23.8 mm ( ,5 /i6 in.). 

Exception to (1) through (5): Devices' or utilization equip- 
ment that is listed to be installed with specified boxes shall be 
permitted. 

314.25 Covers and Canopies. In completed installations, 
each box shall have a cover, faceplate, lampholder, or lu- 
minaire canopy, except where the installation complies with 
410.24(B). 

(A) Nonmetallic or Metal Covers and Plates. Nonmetal- 
lic or metal covers and plates shall be permitted. Where 
metal covers or plates are used, they shall comply with the 
grounding requirements of 250.110. 

Informational Note: For additional grounding requirements, 
see 410.42 for metal luminaire canopies, and 404.12 and 
406.6(B) for metal faceplates. 

(B) Exposed Combustible Wall or Ceiling Finish. Where 
a luminaire canopy or pan is used, any combustible wall or 
ceiling finish exposed between the edge of the canopy or 
pan and the outlet box shall be covered with noncombus- 
tible material. 

(C) Flexible Cord Pendants. Covers of outlet boxes and 
conduit bodies having holes through which flexible cord 
pendants pass shall be provided with bushings designed for 
the purpose or shall have smooth, well-rounded surfaces on 
which the cords may bear. So-called hard rubber or com- 
position bushings shall not be used. 

314.27 Outlet Boxes. 

(A) Boxes at Luminaire or Lampholder Outlets. Ouilet 

boxes oi fi.n lgs de signed ft i the upport of Iv-mm iTes and 
lampholders, and installed as required by 314.23, shall be 
permitti d to support a luminaire or lampholder. 

(1) Wall Outlets. Boxes used at luminaire oi lampholder 
outlets in a wall shall be marked on the interior of the box 
to indicate the maximum weight of the luminaire that is 
permitted to be supported by the box in the wall, if other 
than 23 kg (50 lb). 

Exception: A wall-mounted luminaire or aimp'ioldet weigh- 
ing not more than 3 kg (6 lb) shall be permitted to be sup- 
ported on other boxes or plaster rings that are secured to 
other boxes, provided the luminaire or its supporting yoke, or 
the lampholder, is secured to the box with no fewer than two 
No. 6 or larger screws. 

(2) Ceiling Outlets. At every outlet used exclusively for 
lighting, the box shall be designed or installed so that a 
itimiiuiij oi l.impt'iJur m.iy be attached Boxi shall be 



70-182 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 314.28 



required to support j lumj <uirr weighing a rainimuro of 23 
kg (50 l>>) A lurninaitt (Ml weighs more than is kg (50 Hm 
■■ball be supported independentl) of the outlet box, unless 
the (ti.tlt.t I'D-, is isicd and marked for (he, nia> imum weight 
to be supported. 

(B) Floor Boxes. Boxes listed specifically for this applica- 
tion shall be used for receptacles located in the floor. 

Exception: Where the authority having jurisdiction judges 
them free from likely exposure to physical damage, mois- 
ture, and din, boxes located in elevated floors of show win- 
dows and similar locations shall be permitted to be other than 
those listed for floor applications. Receptacles and covers 
shall be listed as an assembly for this type of location. 

(C) Boxes at Ceiling-Suspended (Paddle) Fan Outlets. 

Outlet boxes or outlet box systems used as the sole support 
of a ceiling-suspended (paddle) fan shall be listed, shall be 
marked by their manufacturer as suitable for this purpose, 
and shall not support ceiling-suspended (paddle) fans that 
weigh more than 32 kg (70 lb). For outlet boxes or outlet box 
systems designed to support ceiling-suspended (paddle) fans 
that weigh more than 16 kg (35 lb), the required marking shall 
include the maximum weight to be supported. 

Where spare separately switched ungrounded conduc- 
tors are pro- ided to a ',.e.l;i£ mounted outlet box, in a 
loc it ion acceptable l'oi a cHling-suspo.ided (raddle) fan ii> 
single or multi-family dwellings. <lir outlet box oi outlet 
box system shall be listed fo, sole support oi a ceiling 
suspended (paddle) fan. 

(D) Utilization Equipment. Boxes used for the support of 
utilization equipment other than ceiling- suspended (paddle) 
fans shall meet the requirements of 314.27(A) for the sup- 
port of a luminaire that is the same size and weight. 

Exception: Utilization equipment weighing not more than 
3 kg (6 lb) shall be permitted to be supported on other 
boxes or plaster rings that are secured to other boxes, pro- 
vided the equipment or its supporting yoke is secured to the 
box with no fewer than two No. 6 or larger screws. 

314.28 Pull and Junction Boxes and Conduit Bodies. 

Boxes and conduit bodies used as pull or junction boxes 
shall comply with 314.28(A) through (E). 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) Minimum Size. For raceways containing conductors 
of 4 AWG or larger that are required to be insulated, and for 
cables containing conductors of 4 AWG or larger, the mini- 
mum dimensions of pull or junction boxes installed in a 
raceway or cable run shall comply with (A)(1) through 
(A)(3). Where an enclosure dimension is to be calculated 
based on the diameter of entering raceways, the diameter 



shall be the metric designator (trade size) expressed in the 
units of measurement employed. 

(1) Straight Pulls. In straight pulls, the length of the box 

>>: ajiduit body shall not be less than eight times the metric 
designator (trade size) of the largest raceway. 

(2) Angle or U Pulls, or Splices. Where splices or where 
angle or U pulls are made, the distance between each race- 
way entry inside the box or conduit body and the opposite 
wall of the box or conduit body shall not be less than six 
times the metric designator (trade size) of the largest race- 
way in a row. This distance shall be increased for additional 
entries by the amount of the sum of the diameters of all other 
raceway entries in the same row on the same wall of the box. 
Each row shall be calculated individually, and the single row 
that provides the maximum distance shall be used. 

Exception: Where a raceway or cable entry is in the wall 
of a box or conduit body opposite a removable cover, the 
distance from that wall to the cover shall be permitted to 
comply with the distance required for one wire per terminal 
in Table 312.6(A). 

The distance between raceway entries enclosing the 
same conductor shall not be less than six times the metric 
designator (trade size) of the larger raceway. 

When transposing cable size into raceway size in 
314.28(A)(1) and (A)(2), the minimum metric designator 
(trade size) raceway required for the number and size of 
conductors in the cable shall be used. 

(3) Smaller Dimensions. Boxes or conduit bodies of di- 
mensions less than those required in 314.28(A)(1) and 
(A)(2) shall be permitted for installations of combinations 
of conductors that are less than the maximum conduit or 
tubing fill (of conduits or tubing being used) permitted by 
Table 1 of Chapter 9, provided the box or conduit body has 
been listed for, and is permanently marked with, the maxi- 
mum number and maximum size of conductors permitted. 

(B) Conductors in Pull or Junction Boxes. In pull boxes 
or junction boxes having any dimension over 1.8 m (6 ft), 
all conductors shall be cabled or racked up in an approved 
manner. 

(C) Covers. All pull boxes, junction boxes, and conduit 
bodies shall be provided with covers compatible with the 
box or conduit body construction and suitable for the con- 
ditions of use. Where used, metal covers shall comply with 
the grounding requirements of 250. 110. 

(D) Permanent Barriers. Where permanent barriers are 
installed in a box, each section shall be considered as a 
separate box. 

(E) Po^.vM-Mbitlii-n liWks. Powq disinb-ifi^r blocks 
shall oc pu'snitteu in pull and |un< 'Jon boxes ovei 1650 cm 3 



2011 Edition NATIONAL ELECTRICAL CODE 



70-183 



314.29 ARTICLE 3 14 — OUTLET, DEVICE. PULL, AND JUNCTION BOXES; CONDUIT BODIES;FITTINGS; AND HANDBOLES 



( 100 in/) for connections of conductors where installed in 
boxes and where the installation complies with (1) through 

(5). 

Exception: Equipment grounding terminal' bars shall be 
permitted in smaller enclosures. 

(1) Installation. Power distribution blocks installed in 
boxes shall be listed. 

(2) Size. In addition to the overall size requirement in the 
first sentence of 314.28(A)(2). the power distribution block 
shall be installed in a box with dimensions no* smallei than 
specified in the installation instruction;, c/ the power dislri- 
bution block. 

(3) Wire Bending Space. Wire bending space at the ter- 
minals of power distribution blocks shall comply with 
312.6. 

(4) Live Parts. Power distribution blocks shall not have 
uninsulated live parts exposed within a box, whether or not 
the box cover is installed. 

(5) Through Conductors. Where the pull or junction 
boxes are used for conductors that do not terminate on the 
power distribution block(s), the through conductors diall be 
arranged so the power distribution block terminals are un- 
obstructed following installation. 

314.29 Boxes, Conduit Bodies, and Handhole Enclo- 
sures to Be Accessible. Boxes, conduit bodies, and hand- 
hole enclosures shall be installed so that the wiring con- 
tained in them can be rendered accessible without removing 
any part of the building or, in underground circuits, without 
excavating sidewalks, paving, earth, or other substance that 
is to be used to establish the finished grade. 

Exception: Listed boxes and handhole enclosures shall be 
permitted where covered by gravel, light aggregate, or non- 
cohesive granulated soil if their location is effectively iden- 
tified and accessible for excavation. 

314.30 Handhole Enclosures. Handhole enclosures shall 
be designed and installed to withstand all loads likely to be 
imposed on them. They shall be identified for use in under- 
ground systems. 

Informational Note: See ANSI/SCTE 77-2002, Specifica- 
tion for Underground Enclosure Integrity, for additional 
information on deliberate and nondeliberate traffic loading 
that can be expected to bear on underground enclosures. 

(A) Size. Handhole enclosures shall be sized in accordance 
with 314.28(A) for conductors operating at 600 volts or 
below, and in accordance with 314.71 for conductors oper- 
ating at over 600 volts. For handhole enclosures without 
bottoms where the provisions of 314.28(A)(2), Exception, 
or 314.71(B)(1), Exception No. 1, apply, the measurement 



to the removable cover shall be taken from the end of the 
conduit or cable assembly. 

(B) Wiring Entries. Underground raceways and cable as- 
semblies entering a handhole enclosure shall extend into 
the enclosure, but they shall not be required to be mechani- 
cally connected to the enclosure. 

(C) Enclosed Wiring. All enclosed conductors and any 
splices or terminations, if present, shall be listed as suitable 
for wet locations. 

(D) Covers. Handhole enclosure covers shall have an iden- 
tifying mark or logo that prominently identifies the function 
of the enclosure, such as "electric." Handhole enclosure 
covers shall require the use of tools to open, or they shall 
weigh over 45 kg (100 lb). Metal covers and other exposed 
conductive surfaces shall be bonded in accordance with 
250.92 if the conductors in the handhole are service con- 
ductors, or in accordance with 250.96(A) if the conductors 
in the handhole are feeder or branch-circuit conductors. 



III. Construction Specifications 

314.40 Metal Boxes, Conduit Bodies, and Fittings. 

(A) Corrosion Resistant. Metal boxes, conduit bodies, 
and fittings shall be corrosion resistant or shall be well- 
galvanized, enameled, or otherwise properly coated inside 
and out to prevent corrosion. 

Informational Note: See 300.6 for limitation in the use of 
boxes and fittings protected from corrosion solely by 
enamel. 

(B) Thickness of Metal. Sheet steel boxes not over 
1650 cm 3 (100 in. 3 ) in size shall be made from steel not less 
than 1.59 mm (0.0625 in.) thick. The wall of a malleable iron 
box or conduit body and a die-cast or permanent-mold cast 
aluminum, brass, bronze, or zinc box or conduit body shall not 
be less than 2.38 mm (%2 in.) thick. Other cast metal boxes or 
conduit bodies shall have a wall thickness not less than 
3.17 mm (Vs in.). 

Exception No. 1: Listed boxes and conduit bodies shown 
to have equivalent strength and characteristics shall be 
permitted to be made of thinner or other metals. 

Exception No. 2: The walls of listed short radius conduit 
bodies, as covered in 314.16(C)(2), shall be permitted to be 
made of thinner meted. 

(C) Metal Boxes Over 1650 cm 3 (100 in. 3 ). Metal boxes 
over 1650 cm 3 (100 in. 3 ) in size shall be constructed so as 
to be of ample strength and rigidity. If of sheet steel, the 
metal thickness shall not be less than 1.35 mm (0.053 in.) 
uncoated. 



70-1 84 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 314 — OUTLET, DEVICE, PULL, AND JUNCTION BOXES; CONDUIT B0DIES;F1TTINGS; AND HANDBOLES 314.71 



(D) Grounding Provisions. A means shall be provided in 
each metal box for the connection of an equipment ground- 
ing conductor. The means shall be permitted to be a tapped 
hole or equivalent. 

314.41 Covers. Metal covers shall be of the same material 
as the box or conduit body with which they are used, or 
they shall be lined with firmly attached insulating material 
that is not less than 0.79 mm (Vm in.) thick, or they shall be 
listed for the purpose. Metal covers shall be the same thick- 
ness as the boxes or conduit body for which they are used, 
or they shall be listed for the purpose. Covers of porcelain 
or other approved insulating materials shall be permitted if 
of such form and thickness as to afford the required protec- 
tion and strength. 

314.42 Bushings. Covers of outlet boxes and conduit bod- 
ies having holes through which flexible cord pendants may 
pass shall be provided with approved bushings or shall 
have smooth, well-rounded surfaces on which the cord may 
bear. Where individual conductors pass through a metal 
cover, a separate hole equipped with a bushing of suitable 
insulating material shall be provided for each conductor. 
Such separate holes shall be connected by a slot as required 
by 300.20. 

314.43 Nonmetallic Boxes. Provisions for supports or 
other mounting means for nonmetallic boxes shall be out- 
side of the box, or the box shall be constructed so as to 
prevent contact between the conductors in the box and the 
supporting screws. 

314.44 Marking. All boxes and conduit bodies, covers, ex- 
tension rings, plaster rings, and the like shall be durably and 
legibly marked with the manufacturer's name or trademark. 

IV. Pull and Junction Boxes, Conduit Bodies, and 
Handlioli Enclosures for Use on Systems over 600 
Volts, Nominal 

314.70 General. 

(A) Pull and Junction ,H<»\es. Where pull and junction 
boxes are used on systems over 600 volts, the installation 
shall comply with the provisions of Part IV and wilh the 
following general provisions of this article: 

(1) Parti, 314.2; 314.3; and 314.4 

(2) Part II, 314.15; 314.17; 314.20; 314.23(A), (B), or (G); 
314.28(B); and 314.29 

(3) Part III, 314.40(A) and (C){ and 314.41 

(B) Condnir Bodie*. Where conduil bodies are used on 
system o\ei 600 \ <lt r , rise tuMiJl.'ttiCb -JiaiJ :omply with 
th provisions of Pari IV and with thi following general 
provisions of this article: 



(1) Parti, 314.4 

(2) Part II. 314.15; 314.17; 314.23(A), (E), or (G); and 
314.29 

(3) Part 111, 314.40(A); and 314.41 

(C) Handht/le Csiciysturs. Where handhole enclosures are 
used on ;ystemsover 600 volts the installation -hull com- 
ply with the provisions of Part IV and -villi the following 
general provisions oi L 1 !-- article: 

(1) Part I 314.3; and 314.4 

(2) Part II. 314. 15: 314.17; 314.23(G); 314.28(B); 314.29; 
and 314.30 

314.71 Size of Pull and Junction Boxes, Conduil Bodies, 
and Handhole Enclosures. Pull and junction boxes and 
handhole enclosures shall provide adequate space and di- 
mensions for the installation of conductors, and they shall 
comply with the specific requirements of this section. Con- 
duit bodies shall i .>.» perm iVd il thej meet i'i> limen i< nal 
requirements fot boxes. 

Exception: Terminal housings supplied with motors shall 
comply with the provisions of 430.12. 

(A) For Straight Pulls. The length of the box shall not be 
less than 48 times the outside diameter, over sheath, of the 
largest shielded or lead-covered conductor or cable entering 
the box. The length shall not be less than 32 times the outside 
diameter of the largest nonshielded conductor or cable. 

(B) For Angle or U Pulls. 

(1) Distance to Opposite Wall. The distance between each 
cable or conductor entry inside the box and the opposite 
wall of the box shall not be less than 36 times the outside 
diameter, over sheath, of the largest cable or conductor. 
This distance shall be increased for additional entries by the 
amount of the sum of the outside diameters, over sheath, of 
all other cables or conductor entries through the same wall 
of the box. 

Exception No. 1: Where a conductor or cable entry is in 
the wall of a box opposite a removable cover, the distance 
from that wall to the cover shall be permitted to be not less 
than the bending radius for the conductors as provided in 
300.34. 

Exception No. 2: Where cables are nonshielded and not 
lead covered, the distance of 36 times the outside diameter 
shall be permitted to be reduced to 24 times the outside 
diameter. 

(2) Distance Between Entry and Exit. The distance be- 
tween a cable or conductor entry and its exit from the box 
shall not be less than 36 times the outside diameter, over 
sheath, of that cable or conductor. 



2011 Edition 



NATIONAL ELECTRICAL. CODE 



70-185 



314.72 



ARTICLE 320 — ARMORED CABLE: TYPE AC 



Exception: Where cables are nonshielded and not lead 
covered, the distance of 36 times the outside diameter shall 
be permitted to be reduced to 24 times the outside diameter. 

(C) Removable Sides. One or more sides of any pull box 
shall be removable. 

314.72 Construction and Installation Requirements. 

(A) Corrosion Protection. Boxes shall be made of mate- 
rial inherently resistant to corrosion or shall be suitably 
protected, both internally and externally, by enameling, gal- 
vanizing, plating, or other means. 

(B) Passing Through Partitions. Suitable bushings, shields, 
or fittings having smooth, rounded edges shall be provided 
where conductors or cables pass through partitions and at 
other locations where necessary. 

(C) Complete Enclosure. Boxes shall provide a complete 
enclosure for the contained conductors or cables. 

(D) Wiring Is Accessible. Boxes and conduit bodies shall 
be installed so that the conductors are accessible without 
removing any fixed part of the building or structure. Work- 
ing space shall be provided in accordance with 110.34. 

(E) Suitable Covers. Boxes shall be closed by suitable 
covers securely fastened in place. Underground box covers 
that weigh over 45 kg (100 lb) shall be considered meeting 
this requirement. Covers for boxes shall be permanently 
marked "DANGER — HIGH VOLTAGE — KEEP OUT." 
The marking shall be on the outside of the box cover and 
shall be readily visible. Letters shall be block type and at 
least 13 mm (Vi in.) in height. 

(F) Suitable for Expected Handling. Boxes and their 
covers shall be capable of withstanding the handling to 
which they are likely to be subjected. 



II. Installation 

320.10 Uses Permitted. Type AC cable shall be permitted 
as follows: 

(1) For feeders and branch circuits in both exposed and 
concealed installations 

(2) In cable trays 

(3) In dry locations 

(4) Embedded in plaster finish on brick or other masonry, 
except in damp or wet locations 

(5) To be run or fished in the air voids of masonry block or 
tile walls where such walls are not exposed or subject 
to excessive moisture or dampness 



Informational Note: 
inclusive list. 



The "Uses Permitted" is not an all- 



320.12 Uses Not Permitted. Type AC cable shall not be 
used as follows: 

(1) Where subject to physical damage 

(2) In damp or wet locations 

(3) In air voids of masonry block or tile walls where such 
walls are exposed or subject to excessive moisture or 
dampness 

(4) Where exposed to corrosive conditions 

(5) Embedded in plaster finish on brick or other masonry 
in damp or wet locations 

320.15 Exposed Work. Exposed runs of cable, except as 
provided in 300.11(A), shall closely follow the surface of 
the building finish or of running boards. Exposed runs shall 
also be permitted to be installed on the underside of joists 
where supported at each joist and located so as not to be 
subject to physical damage. 

320.17 Through or Parallel to Framing Members. Type 
AC cable shall be protected in accordance with 300.4(A), 
(C), and (D) where installed through or parallel to framing 
members. 



ARTICLE 320 
Armored Cable: Type AC 



I. General 



320.1 Scope. This article covers the use, installation, and 
construction specifications for armored cable, Type AC. 

320.2 Definition. 

Armored Cable, Type AC. A fabricated assembly of insu- 
lated conductors in a flexible interlocked metallic armor. 
See 320.100. 



320.23 In Accessible Attics. Type AC cables in accessible 
attics or roof spaces shall be installed as specified in 
320.23(A) and (B). 

(A) Cables Run Across the Top of Floor Joists. Where 
run across the top of floor joists, or within 2.1 m (7 ft) of 
the floor or floor joists across the face of rafters or studding, 
the cable shall be protected by substantial guard strips that 
are at least as high as the cable. Where this space is not 
accessible by permanent stairs or ladders, protection shall 
only be required within 1.8 m (6 ft) of the nearest edge of 
the scuttle hole or attic entrance. 

(B) Cable Installed Parallel to Framing Members. 

Where the cable is installed parallel to the sides of rafters, 



70-186 



NATIONAL ELECTRICAL CODE 2011 Edilion 



ARTICLE 322 — FLAT CABLE ASSEMBLIES: TYPE FC 



322.1 



studs, or ceiling or floor joists, neither guard strips nor 
running boards shall be required, and the installation shall 
also comply with 300.4(D). 

320.24 Bending Radius. Bends in Type AC cable shall be 
made such that the cable is not damaged. The radius of the 
curve of the inner edge of any bend shall not be less than 
five times the diameter of the Type AC cable. 

320.30 Securing and Supporting. 

(A) General. Type AC cable shall be supported and se- 
cured by staples, cable ties, straps, hangers, or similar fit- 
tings, designed and installed so as not to damage the cable. 

(B) Securing. Unless otherwise permitted. Type AC cable 
shall be secured within 300 mm (12 in.) of every outlet 
box, junction box, cabinet, or fitting and at intervals not 
exceeding 1.4 m (4'A ft) where installed on or across fram- 
ing members. 

(C) Supporting. Unless otherwise permitted. Type AC 
cable shall be supported at intervals not exceeding 1.4 m 
(4'/2 ft). 

Horizontal runs of Type AC cable installed in wooden 
or metal framing members or similar supporting means 
shall be considered supported where such support does not 
exceed 1.4-m (4 '/i-ft) intervals. 

(D) Unsupported Cables. Type AC cable shall be permit- 
ted to be unsupported where the cable complies with any of 
the following: 

(1) Is fished between access points through concealed 
spaces in finished buildings or structures and support- 
ing is impracticable 

(2) Is not more than 600 mm (2 ft) in length at terminals 
where flexibility is necessary 

(3) Is not more than 1 .8 m (6 ft) in length from the last 
point of cable support to the point of connection to a 
luminaire(s) or other electrical equipment and the cable 
and point of connection are within an accessible ceil- 
ing. For the purposes of this section, Type AC cable 
fittings shall be permitted as a means of cable support. 

320.40 Boxes and Fittings. At all points where the armor 
of AC cable terminates, a fitting shall be provided to protect 
wires from abrasion, unless the design of the outlet boxes 
or fittings is such as to afford equivalent protection, and, in 
addition, an insulating bushing or its equivalent protection 
shall be provided between the conductors and the armor. 
The connector or clamp by which the Type AC cable is 
fastened to boxes or cabinets shall be of such design that 
the insulating bushing or its equivalent will be visible for 
inspection. Where change is made from Type AC cable to 
other cable or raceway wiring methods, a box, fitting, or 



conduit body shall be installed at junction points as re- 
quired in 300.15. 

320.80 Ampacity. The ampacity shall be determined in 
accordance with 310.15. 

(A) Thermal Insulation. Armored cable installed in ther- 
mal insulation shall have conductors rated at 90°C (194°F). 
The ampacity of cable installed in these applications shall 
not exceed that of a 60°C (140 C F) rated conductor. The 
90°C (194°F) rating shall be permitted to be used for am- 
pacity adjustment and correction calculations; however, the 
ampacity shall not exceed that of a 60°C (140°F) rated 
conductor. 

(B) Cable Tray. The ampacity of Type AC cable installed in 
cable tray shall be determined in accordance with 392.80(A). 

III. Construction Specifications 

320.100 Construction. Type AC cable shall have an armor 
of flexible metal tape and shall have an internal bonding 
strip of copper or aluminum in intimate contact with the 
armor for its entire length. 

320.104 Conductors. Insulated conductors shall be of a 
type listed in Table 310. 104(A) or those identified for use in 
this cable. In addition, the conductors shall have an overall 
moisture-resistant and fire-retardant fibrous covering. For 
Type ACT, a moisture-resistant fibrous covering shall be 
required only on the individual conductors. 

320.108 Equipment Grounding Conductor. Type AC cable 
shall provide an adequate path for fault current as required 
by 250.4(A)(5) or (B)(4) to act as an equipment grounding 
conductor. 

320.120 Marking. The cable shall be marked in accor- 
dance with 310.120, except that Type AC shall have ready 
identification of the manufacturer by distinctive external 
markings on the cable armor throughout its entire length. 



ARTICLE 322 

Flat Cable Assemblies: Type FC 



I. General 

322.1 Scope. This article covers the use, installation, and 
construction specifications for flat cable assemblies, Type FC. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-187 



322.2 



ARTICLE 322 — FLAT CABLE ASSEMBLIES: TYPE FC 



322.2 Definition. 

Flat Cable Assembly, Type FC. An assembly of parallel 
conductors formed integrally with an insulating material 
web specifically designed for field installation in surface 
metal raceway. 

II. Installation 

322.10 Uses Permitted. Flat cable assemblies shall be per- 
mitted only as follows: 

(1) As branch circuits to supply suitable tap devices for light- 
ing, small appliances, or small power loads. The rating of 
the branch circuit shall not exceed 30 amperes. 

(2) Where installed for exposed work. 

(3) In locations where they will not be subjected to physi- 
cal damage. Where a flat cable assembly is installed 
less than 2.5 m (8 ft) above the floor or fixed working 
platform, it shall be protected by a cover identified for 
the use. 

(4) In surface metal raceways identified for the use. The 
channel portion of the surface metal raceway systems 
shall be installed as complete systems before the flat 
cable assemblies are pulled into the raceways. 

322.12 Uses Not Permitted. Flat cable assemblies shall 
not be used as follows: 

(1) Where exposed to corrosive cori'hnnns. unless suitable 
for the application 

(2) In hoistways or on elevators or escalators 

(3) In any hazardous (classified) location, except ,is spe- 
cifically permitted by othei articles in this Code 

(4) Outdoors or in wet or damp locations unless identified 
for the use 

322.30 Securing and Supporting. The flat cable assem- 
blies shall be supported by means of their special design 
features, within the surface metal raceways. 

The surface metal raceways shall be supported as re- 
quired for the specific raceway to be installed. 

322.40 Boxes and Fittings. 

(A) Dead Ends. Each flat cable assembly dead end shall 
be terminated in an end-cap device identified for the use. 

The dead-end fitting for the enclosing surface metal 
raceway shall be identified for the use. 

(B) Luminaire Hangers. Luminaire hangers installed with 
the flat cable assemblies shall be identified for the use. 

(C) Fittings. Fittings to be installed with flat cable assem- 
blies shall be designed and installed to prevent physical 
damage to the cable assemblies. 



(D) Extensions. All extensions from flat cable assemblies 
shall be made by approved wiring methods, within the 
junction boxes, installed at either end of the flat cable as- 
sembly runs. 

322.56 Splices and Taps. 

(A) Splices. Splices shall be made in listed junction boxes. 

(B) Taps. Taps shall be made between any phase conduc- 
tor and the grounded conductor or any other phase conduc- 
tor by means of devices and fittings identified for the use. 
Tap devices shall be rated at not less than 15 amperes, or 
more than 300 volts to ground, and shall be color-coded in 
accordance with the requirements of 322.120(C). 

III. Construction 

322.100 Construction. Flat cable assemblies shall consist 
of two, three, four, or five conductors. 

322.104 Conductors. Flat cable assemblies shall have 
conductors of 1 AWG special stranded copper wires. 

322.112 Insulation. The entire flat cable assembly shall be 
formed to provide a suitable insulation covering all the 
conductors and using one of the materials recognized in 
Table 310.104(A) for general branch-circuit wiring. 

322.120 Marking. 

(A) Temperature Rating. In addition to the provisions of 
310.120, Type FC cable shall have the temperature rating 
durably marked on the surface at intervals not exceeding 
600 mm (24 in.). 

(B) Identification of Grounded Conductor. The grounded 
conductor shall be identified throughout its length by means of 
a distinctive and durable white or gray marking. 

Informational Note: The color gray may have been used in 
the past as an ungrounded conductor. Care should be taken 
when working on existing systems. 

(C) Terminal Block Identification. Terminal blocks iden- 
tified for the use shall have distinctive and durable mark- 
ings for color or word coding. The grounded conductor 
section shall have a white marking or other suitable desig- 
nation. The next adjacent section of the terminal block shall 
have a black marking or other suitable designation. The 
next section shall have a red marking or other suitable 
designation. The final or outer section, opposite the 
grounded conductor section of the terminal block, shall 
have a blue marking or other suitable designation. 



70- li 



NATIONAL ELECTRICAL CODE 20 1 1 Edition 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



324.40 



ARTICLE 324 
Flat Conductor Cable: Type FCC 



I. General 

324.1 Scope. This article covers a field-installed wiring 
system for branch circuits incorporating Type FCC cable 
and associated accessories as denned by the article. The 
wiring system is designed for installation under carpet 
squares. 

324.2 Definitions. 

Bottom Shield. A protective layer that is installed between 
the floor and Type FCC flat conductor cable to protect the 
cable from physical damage and may or may not be incor- 
porated as an integral part of the cable. 

Cable Connector. A connector designed to join Type FCC 
cables without using a junction box. 

FCC System. A complete wiring system for branch circuits 
that is designed for installation under carpet squares. The FCC 
system includes Type FCC cable and associated shielding, 
connectors, terminators, adapters, boxes, and receptacles. 

Insulating End. An insulator designed to electrically insu- 
late the end of a Type FCC cable. 

Metal Shield Connections. Means of connection designed 
to electrically and mechanically connect a metal shield to 
another metal shield, to a receptacle housing or self- 
contained device, or to a transition assembly. 

Top Shield. A grounded metal shield covering under-carpet 
components of the FCC system for the purposes of provid- 
ing protection against physical damage. 

Transition Assembly. An assembly to facilitate connection 
of the FCC system to other wiring systems, incorporating 
(1) a means of electrical interconnection and (2) a suitable 
box or covering for providing electrical safety and protec- 
tion against physical damage. 

Type FCC Cable. Three or more flat copper conductors 
placed edge-to-edge and separated and enclosed within an 
insulating assembly. 

324.6 Listing Requirements. Type FCC cable and associ- 
ated fittings shall be listed. 

II. Installation 

324.10 Uses Permitted. 

(A) Branch Circuits. Use of FCC systems shall be permit- 
ted both for general -purpose and appliance branch circuits 
and for individual branch circuits. 



(B) Branch- Circuit Ratings. 

(1) Voltage. Voltage between ungrounded conductors shall 
not exceed 300 volts. Voltage between ungrounded conduc- 
tors and the grounded conductor shall not exceed 150 volts. 

(2) Current. General-purpose and appliance branch circuits 
shall have ratings not exceeding 20 amperes. Individual 
branch circuits shall have ratings not exceeding 30 amperes. 

(C) Floors. Use of FCC systems shall be permitted on 
hard, sound, smooth, continuous floor surfaces made of 
concrete, ceramic, or composition flooring, wood, and simi- 
lar materials. 

(D) Walls. Use of FCC systems shall be permitted on wall 
surfaces in surface metal raceways. 

(E) Damp Locations. Use of FCC systems in damp loca- 
tions shall be permitted. 

(F) Heated Floors. Materials used for floors heated in ex- 
cess of 30°C (86°F) shall be identified as suitable for use at 
these temperatures. 

(G) System Height. Any portion of an FCC system with a 
height above floor level exceeding 2.3 mm (0.090 in.) shall 
be tapered or feathered at the edges to floor level. 

324.12 Uses Not Permitted. FCC systems shall not be 
used in the following locations: 

(1) Outdoors or in wet locations 

(2) Where subject to corrosive vapors 

(3) In any hazardous (classified) location 

(4) In residential, school, and hospital buildings 

324.18 Crossings. Crossings of more than two Type FCC 
cable runs shall not be permitted at any one point. Cross- 
ings of a Type FCC cable over or under a flat communica- 
tions or signal cable shall be permitted. In each case, a 
grounded layer of metal shielding shall separate the two 
cables, and crossings of more than two flat cables shall not 
be permitted at any one point. 

324.30 Securing and Supporting. All FCC system com- 
ponents shall be firmly anchored to the floor or wall using 
an adhesive or mechanical anchoring system identified for 
this use. Floors shall be prepared to ensure adherence of the 
FCC system to the floor until the carpet squares are placed. 

324.40 Boxes and Fittings. 

(A) Cable Connections and Insulating Ends. All Type 
FCC cable connections shall use connectors identified for their 
use, installed such that electrical continuity, insulation, and 
sealing against dampness and liquid spillage are provided. All 



201 1 Edition 



NATIONAL ELECTRICAL CODE 



70-189 



324.41 



ARTICLE 324 — FLAT CONDUCTOR CABLE: TYPE FCC 



bare cable ends shall be insulated and sealed against dampness 
and liquid spillage using listed insulating ends. 

(B) Polarization of Connections. All receptacles and con- 
nections shall be constructed and installed so as to maintain 
proper polarization of the system. 

(C) Shields. 

(1) Top Shield. A metal top shield shall be installed over 
all floor-mounted Type FCC cable, connectors, and insulat- 
ing ends. The top shield shall completely cover all cable 
runs, corners, connectors, and ends. 

(2) Bottom Shield. A bottom shield shall be installed be- 
neath all Type FCC cable, connectors, and insulating ends. 

(D) Connection to Other Systems. Power feed, grounding 
connection, and shield system connection between the FCC 
system and other wiring systems shall be accomplished in a 
transition assembly identified for this use. 

(E) Metal-Shield Connectors. Metal shields shall be con- 
nected to each other and to boxes, receptacle housings, 
self-contained devices, and transition assemblies using 
metal-shield connectors. 

324.41 Floor Coverings. Floor-mounted Type FCC cable, 
cable connectors, and insulating ends shall be covered with 
carpet squares not larger than 914 mm (36 in.) square. 
Carpet squares that are adhered to the floor shall be at- 
tached with release-type adhesives. 

324.42 Devices. 

(A) Receptacles. All receptacles, receptacle housings, and 
self-contained devices used with the FCC system shall be 
identified for this use and shall be connected to the Type 
FCC cable and metal shields. Connection from any ground- 
ing conductor of the Type FCC cable shall be made to the 
shield system at each receptacle. 

(B) Receptacles and Housings. Receptacle housings and 
self-contained devices designed either for floor mounting or 
for in-wall or on-wall mounting shall be permitted for use with 
the FCC system. Receptacle housings and self-contained de- 
vices shall incorporate means for facilitating entry and termi- 
nation of Type FCC cable and for electrically connecting the 
housing or device with the metal shield. Receptacles and self- 
contained devices shall comply with 406.4. Power and com- 
munications outlets installed together in common housing 
shall be permitted in accordance with 800.133(A)(1)(c), Ex- 
ception No. 2. 

324.56 Splices and Taps. 

(A) FCC Systems Alterations. Alterations to FCC sys- 
tems shall be permitted. New cable connectors shall be 



used at new connection points to make alterations. It shall 
be permitted to leave unused cable runs and associated 
cable connectors in place and energized. All cable ends 
shall be covered with insulating ends. 

(B) Transition Assemblies. All transition assemblies shall 
be identified for their use. Each assembly shall incorporate 
means for facilitating entry of the Type FCC cable into the 
assembly, for connecting the Type FCC cable to grounded 
conductors, and for electrically connecting the assembly to the 
metal cable shields and to equipment grounding conductors. 

324.60 Grounding. All metal shields, boxes, receptacle 
housings, and self-contained devices shall be electrically 
continuous to the equipment grounding conductor of the 
supplying branch circuit. All such electrical connections 
shall be made with connectors identified for this use. The 
electrical resistivity of such shield system shall not be more 
than that of one conductor of the Type FCC cable used in 
the installation. 

III. Construction 

324.100 Construction. 

(A) Type FCC Cable. Type FCC cable shall be listed for 
use with the FCC system and shall consist of three, four, or 
five flat copper conductors, one of which shall be an equip- 
ment grounding conductor. 

(B) Shields. 

(1) Materials and Dimensions. All top and bottom shields 
shall be of designs and materials identified for their use. 
Top shields shall be metal. Both metallic and nonmetallic 
materials shall be permitted for bottom shields. 

(2) Resistivity. Metal shields shall have cross-sectional ar- 
eas that provide for electrical resistivity of not more than 
that of one conductor of the Type FCC cable used in the 
installation. 

324.101 Corrosion Resistance. Metal components of the 
system shall be either corrosion resistant, coated with 
corrosion -resistant materials, or. insulated from contact with 
corrosive substances. 

324.112 Insulation. The insulating material of the cable 
shall be moisture resistant and flame retardant. All insulating 
materials in the FCC systems shall be identified for their use. 

324.120 Markings. 

(A) Cable Marking. Type FCC cable shall be clearly and 
durably marked on both sides at intervals of not more than 
610 mm (24 in.) with the information required by 310.120(A) 
and with the following additional information: 



70-190 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 326 — INTEGRATED GAS SPACER CABLE: TYPE IGS 



326.112 



(1) Material of conductors 

(2) Maximum temperature rating 

(3) Ampacity 

(B) Conductor Identification. Conductors shall be clearly 
and durably identified on both sides throughout their length 
as specified in 310.110. 



Table 326.24 Minimum Radii of Bends 



Conduit Size 


Minimum Radii 


Metric Designator 


Trade Size 


mm in. 


53 

78 

103 


2 
3 

4 


600 24 
900 35 
1 150 45 



ARTICLE 326 
Integrated Gas Spacer Cable: Type IGS 

I. General 

326.1 Scope. This article covers the use, installation, and 
construction specifications for integrated gas spacer cable, 
Type TGS. 

326.2 Definition. 

Integrated Gas Spacer Cable, Type IGS. A factory assem- 
bly of one or more conductors, each individually insulated and 
enclosed in a loose fit, nonmetallic flexible conduit as an in- 
tegrated gas spacer cable rated through 600 volts. 

II. Installation 

326.10 Uses Permitted. Type IGS cable shall be permitted 
for use under ground, including direct burial in the earth, as 
the following: 

(1) Service-entrance conductors 

(2) Feeder or branch-circuit conductors 

(3) Service-lateral conductors 

326.12 Uses Not Permitted. Type IGS cable shall not be 
used as interior wiring or be exposed in contact with buildings. 

326.24 Bending Radius. Where the coilable nonmetallic 
conduit and cable is bent for installation purposes or is 
flexed or bent during shipment or installation, the radii of 
bends measured to the inside of the bend shall not be less 
than specified in Table 326.24. 

326.26 Bends. A run of Type IGS cable between pull boxes 
or terminations shall not contain more than the equivalent of 
four quarter bends (360 degrees total), including those bends 
located immediately at the pull box or terminations. 

326.40 Fittings. Terminations and splices for Type IGS 
cable shall be identified as a type that is suitable for main- 



taining the gas pressure within the conduit. A valve and cap 
shall be provided for each length of the cable and conduit 
to check the gas pressure or to inject gas into the conduit. 

326.80 Ampacity. The ampacity of Type IGS cable shall 
not exceed the values shown in Table 326.80. 



Table 326.80 


Ampacity of Type IGS Cable 




Size (kcmi 


) Amperes 


Size (kcmil) 


Amperes 


250 


119 


2500 


376 


500 


168 


3000 


412 


750 


206 


3250 


429 


1000 


238 


3500 


445 


1250 


266 


3750 


461 


1500 


292 


4000 


476 


1750 


315 


4250 


491 


2000 


336 


4500 


505 


2250 


357 


4750 


519 



III. Construction Specifications 

326.104 Conductors. The conductors shall be solid alumi- 
num rods, laid parallel, consisting of one to nineteen 
12.7 mm ( [ A> in.) diameter rods. The minimum conductor 
size shall be 250 kcmil, and the maximum size shall be 
4750 kcmil. 

326.112 Insulation. The insulation shall be dry kraft paper 
tapes and a pressurized sulfur hexafluoride gas (SF 6 ), both 
approved for electrical use. The nominal gas pressure shall 
be 138 kPa gauge (20 lb/in. 2 gauge). The thickness of the 
paper spacer shall be as specified in Table 326.112. 



Table 326.112 Paper Spacer 


Thickness 








Thickness 






Size (kcmil) 


mm 


in. 




250-1000 
1250-4750 


1.02 
1.52 


0.040 
0.060 





2011 Edition 



NATIONAL ELECTRICAL CODE 



70-191 



326.116 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



326.116 Conduit. The conduit shall be a medium density 
polyethylene identified as suitable for use with natural gas 
rated pipe in metric designator 53, 78, or 103 (trade size 2, 
3, or 4). The percent fill dimensions for the conduit are 
shown in Table 326.116. 

The size of the conduit permitted for each conductor 
size shall be calculated for a percent fill not to exceed those 
found in Table 1, Chapter 9. 

Table 326.116 Conduit Dimensions 





Actual 


Actual 




Outside 


Inside 


Conduit Size 


Diameter 


Diameter 



Metric Trade 
Designator Size 



mm 



in. 



53 


2 


60 


2.375 


49.46 


1.947 


78 


3 


89 


3.500 


73.30 


2.886 


103 


4 


114 


4.500 


94.23 


3.710 



326.120 Marking. The cable shall be marked in accor- 
dance with 310.120(A), 310.120(B)(1), and 310.120(D). 



ARTICLE 328 
Medium Voltage Cable: Type MY 



I. General 

328.1 Scope. This article covers the use, installation, and 
construction specifications for medium voltage cable, 
Type MV. 

328.2 Definition. 

Medium Voltage Cable, Type MV. A single or multicon- 
ductor solid dielectric insulated cable rated 2001 volts or 
higher. 

II. Installation 

328.10 Uses Permitted. Type MV cable shall be permitted 
for use on power systems rated up to and including 35,000 
volts, nominal, as follows: 

(1) In wet or dry locations. 

(2) In raceways. 

(3) In cable trays, where identified for the use, in accordance 
with 392.10, 392.20iR). (C). and CD), 392.22(C), 
392.30(B)(1), 392.46, 392.56. cud 392.60. Type MV 
cable that has an overall metallic sheath oi armor, core- 
plies with the requiiements for Type MC cable ai d is 



identified as ' MV ot MC" shall be permiued to be in- 
stalled in cable trays in accordance with 392.10(B)(2). 

(4) Direct buried in accordance with 300.50. 

(5) In messenger-supported wiring in accordance with Part 
II of Article 396. 

(6) As exposed runs in accordance with 300.37. Type >IV 
cable thai h is in overall me a! lie sheath i • armc r, <'m 
plies with the requirements lor I /[»- MC table, and is 
identified as "MV or MC*' shall be permitted to be 
installed as exposed runs oi metal-clad cable in accoi 
dance with 300.37. 

Informational Note: The "Uses Permitted" is not an all- 
inclusive list. 

328.12 Uses Not Permitted. Type MV cable shall not be 
used where exposed to direct sunlight, unless identified for 
the use. 

328.14 Installation. Type MV cable shall be installed, ter- 
mini ted, and tested h- qualified persons. 

Informational Note: IEEE 5 76-WQQ, Recommended Prat - 
tice foi Installation Termination, and Testing of Insulated 
P wef i ah>'\ as ' fed. in industrial and Cotnrnt ial Ap 
plications, a.i - hj<ie.. installation inlomuri^n - ;nd testing t ri- 
teria for MV cable. 

328.80 Ampacity. The ampacity of Type MV cable shall 
be determined in accordance with 310.60. The ampacity of 
Type MV cable installed in cable tray shall be determined 
in accordance with 392.80(B). 

III. Construction Specifications 

328.100 Construction. Type MV cables shall have copper, 
aluminum, or copper-clad aluminum conductors and shall 
comply with Table 310.104(C) and Table 310.104(D) or 
Table 310.104(E). 

328.120 Marking. Medium voltage cable shall be marked 
as required by 310.120. 



ARTICLE 330 
Metal-Clad Cable: Type MC 



I. General 

330.1 Scope. This article covers the use, installation, and 
construction specifications of metal-clad cable, Type MC. 



70-192 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 330 — METAL-CLAD CABLE: TYPE MC 



330.24 



330.2 Definition. 

Metal Clad Cable, Type MC. A factory assembly of one 
or more insulated circuit conductors with or without optical 
fiber members enclosed in an armor of interlocking metal 
tape, or a smooth or corrugated metallic sheath. 

II. Installation 

330.10 Uses Permitted. 

(A) General Uses. Type MC cable shall be permitted as 
follows: 

(1) For services, feeders, and branch circuits. 

(2) For power, lighting, control, and signal circuits. 

(3) Indoors or outdoors. 

(4) Exposed or concealed. 

(5) To be direct buried where identified for such use. 

(6) In cable tray where identified for such use. 

(7) In any raceway. 

(8) As aerial cable on a messenger. 

(9) In hazardous (classified) locations where specilicalh 
permitted by oLhcr articles in this Code. 

(10) In dry locations and embedded in plaster finish on brick 
or other masonry except in damp or wet locations. 

(11) In wet locations where any of the following condi- 
tions are met: 

a. The metallic covering is impervious to moisture. 

b. A moisture-impervious jacket is provided under 
the metal covering. 

c. The insulated conductors under the metallic covering 
are listed for use in wet locations, and a corrosion- 
resistant jacket is provided over the metallic sheath. 

(12) Where single-conductor cables are used, all phase 
conductors and, where used, the grounded conductor 
shall be grouped together to minimize induced voltage 
on the sheath. 

(B) Specific Uses. Type MC cable shall be permitted to be 
installed in compliance with Pails II and III of Article 725 and 
770.133 as applicable and in accordance with 330.10(B)(1) 
through (B)(4). 

(1) Cable Tray. Type MC cable installed in cable tray shall 
comply with 392.10, 392.12, 392.18, 392.20, 392.22, 
392.30, 392.46, 392.56, 392.60(C), and 392.80. 

(2) Direct Buried. Direct-buried cable shall comply with 
300.5 or 300.50, as appropriate. 

(3) Installed as Service-Entrance Cable. Type MC cable 
installed as service-entrance cable shall be permitted in ac- 
cordance with 230.43. 



(4) Installed Outside of Buildings or Structures or as 
Aerial Cable. Type MC cable installed outside of buildings 
or structures or as aerial cable shall comply with 225.10, 
396.10, and 396.12. 



Informational Note: 
inclusive list. 



The "Uses Permitted" is not an all- 



330.12 Uses Not Permitted. Type MC cable shall not be 
used under either of the following conditions: 

(1) Where subject to physical damage 

(2) Where exposed to any of the destructive corrosive con- 
ditions in (a) or (b), unless the metallic sheath or armor 
is resistant to the conditions or is protected by material 
resistant to the conditions: 

a. Direct buried in the earth or embedded in concrete 
unless identified for direct burial 

b. Exposed to cinder fills, strong chlorides, caustic al- 
kalis, or vapors of chlorine or of hydrochloric acids 

330.17 Through or Parallel to Framing Members. Type 
MC cable shall be protected in accordance with 300.4(A), 
(C), and (D) where installed through or parallel to framing 
members. 

330.23 In Accessible Attics. The installation of Type MC 
cable in accessible attics or roof spaces shall also comply 
with 320.23. 

330.24 Bending Radius. Bends in Type MC cable shall be 
so made that the cable will not be damaged. The radius of 
the curve of the inner edge of any bend shall not be less 
than required in 330.24(A) through (C). 

(A) Smooth Sheath. 

(1) Ten times the external diameter of the metallic sheath 
for cable not more than 19 mm (% in.) in external 
diameter 

(2) Twelve times the external diameter of the metallic 
sheath for cable more than 19 mm ( 3 A in.) but not more 
than 38 mm {VA in.) in external diameter 

(3) Fifteen times the external diameter of the metallic 
sheath for cable more than 38 mm (1 Vi in.) in external 
diameter 

(B) Interlocked-Type Armor or Corrugated Sheath. 

Seven times the external diameter of the metallic sheath. 

(C) Shielded Conductors. Twelve times the overall diam- 
eter of one of the individual conductors or seven times the 
overall diameter of the multiconductor cable, whichever is 
greater. 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-193 



330.30 



ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 



330.30 Securing and Supporting. 

(A) General. Type MC cable shall be supported and se- 
cured by staples, cable ties, straps, hangers, or similar fit- 
tings or other approved means designed and installed so as 
not to damage the cable. 

(B) Securing. Unless otherwise provided, cables shall be 
secured at intervals not exceeding 1.8 m (6 ft). Cables con- 
taining four or fewer conductors sized no larger than 
10 AWG shall be secured within 300 mm (12 in.) of every 
box, cabinet, fitting, or other cable termination. 

(C) Supporting. Unless otherwise provided, cables shall 
be supported at intervals not exceeding 1.8 m (6 ft). 

Horizontal runs of Type MC cable installed in wooden 
or metal framing members or similar supporting means 
shall be considered supported and secured where such sup- 
port does not exceed 1.8-m (6-ft) intervals. 

(D) Unsupported Cables. Type MC cable shall be permit- 
ted to be unsupported where the cable: 

(1) Is fished between access points through concealed spaces 
in finished buildings or structures and supporting is im- 
practical; or 

(2) Is not more than 1.8 m (6 ft) in length from the last 
point of cable support to the point of connection to 
luminaires or other electrical equipment and the cable 
and point of connection are within an accessible ceil- 
ing. For the purpose of this section, Type MC cable 
fittings shall be permitted as a means of cable support. 

330.31 Single Conductors. Where single-conductor cables 
with a nonferrous armor or sheath are used, the installation 
shall comply with 300.20. 

330.40 Boxes and Fittings. Fittings used for connecting 
Type MC cable to boxes, cabinets, or other equipment shall 
be listed and identified for such use. 

330.80 Ampacity. The ampacity of Type MC cable shall 
be determined in accordance with 310.15 or 310.60 for 14 
AWG and larger conductors and in accordance with Table 
402.5 for 18 AWG and 16 AWG conductors. The installa- 
tion shall not exceed the temperature ratings of termina- 
tions and equipment. 

(A) Type MC Cable Installed in Cable Tray. The am- 
pacities for Type MC cable installed in cable tray shall be 
determined in accordance with 392.80. 

(B) Single Type MC Conductors Grouped Together. 

Where single Type MC conductors are grouped together in 
a triangular or square configuration and installed on a mes- 
senger or exposed with a maintained free airspace of not 
less than 2.15 times one conductor diameter (2.15 x O.D.) 



of the largest conductor contained within the configuration 
and adjacent conductor configurations or cables, the ampac- 
ity of the conductors shall not exceed the allowable am- 
pacities in the following tables: 

(1) Table 3 10. 15(B)! 20) for conductors rated through 
2000 volts 

(2) Table 310.60(0(67) and Table 310.60(0(68) for con- 
ductors rated over 2000 volts 

III. Construction Specifications 

330.104 Conductors. Conductors shall be of copper, alumi- 
num, copper-clad aluminum, nickel or nickel-coated copper, 
solid or stranded. The minimum conductor size shall be 
18 AWG copper, nickel or nickel-coated copper, Or 12 AWG 
aluminum or copper-clad aluminum. 

330.108 Equipment Grounding Conductor. Where Type 
MC cable is used to provide an equipment grounding con- 
ductor, it shall comply with 250.118(10) and 250.122. 

330.112 Insulation. Insulated conductors shall comply with 
330.112(A) or (B). 

(A) 600 Volts. Insulated conductors in sizes 18 AWG and 
16 AWG shall be of a type listed in Table 402.3, with a maxi- 
mum operating temperature not less than 90°C (194°F) and as 
permitted by 725.49. Conductors larger than 16 AWG shall be 
of a type listed in Table 310.104(A) or of a type identified for 
use in Type MC cable. 

(B) Over 600 Volts. Insulated conductors shall be of a type 
listed in Table 310.1 04( C) through Table 3 1 0. 1 04i h). 

330.116 Sheath. Metallic covering shall be one of the fol- 
lowing types: smooth metallic sheath, corrugated metallic 
sheath, interlocking metal tape armor. The metallic sheath 
shall be continuous and close fitting. A nonmagnetic sheath 
or armor shall be used on single conductor Type MC. 
Supplemental protection of an outer covering of corrosion- 
resistant material shall be permitted and shall be required 
where such protection is needed. The sheath shall not be 
used as a current-carrying conductor. 

Informational Note: See 300.6 for protection against 
corrosion. 



ARTICLE 332 

Mineral Insulated, M etal-Sheathed 

Cable: TYpe MI 

I. General 

332.1 Scope. This article covers the use, installation, and 
construction specifications for mineral-insulated, metal- 
sheathed cable, Type MI. 



70-1 94 



NATIONAL ELECTRICAL CODE 201 1 Edition 



ARTICLE 332 — MINERAL-INSULATED, METAL-SHEATHED CABLE: TYPE MI 



332.80 



332.2 Definition. 

Mineral-Insulated, Metal-Sheathed Cable, Type MI. A 

factory assembly of one or more conductors insulated with 
a highly compressed refractory mineral insulation and en- 
closed in a liquidtight and gastight continuous copper or 
alloy steel sheath. 

II. Installation 

332.10 Uses Permitted. Type MI cable shall be permitted 
as follows: 

(1) For services, feeders, and branch circuits 

(2) For power, lighting, control, and signal circuits 

(3) In dry, wet, or continuously moist locations 

(4) Indoors or outdoors 

(5) Where exposed or concealed 

(6) Where embedded in plaster, concrete, fill, or other 
masonry, whether above or below grade 

(7) In hazardous (classified) locations where specifically 
permitted by other articles in this Code 

(8) Where exposed to oil and gasoline 

(9) Where exposed to corrosive conditions not deteriorat- 
ing to its sheath 

(10) In underground runs where suitably protected against 
physical damage and corrosive conditions 

(11) In or attached to cable tray 

Informational Note: The "Uses Permitted" is not an all- 
inclusive list. 

332.12 Uses Not Permitted. Type MI cable shall not be 
used under the following conditions or in the following 
locations: 

(1) In underground runs unless protected from physical 
damage, where necessary 

(2) Where exposed to conditions that are destructive and 
corrosive to the metallic sheath, unless additional pro- 
tection is provided 

332.17 Through or Parallel to Framing Members. Type 
MI cable shall be protected in accordance with 300.4 where 
installed through or parallel to framing members. 

332.24 Bending Radius. Bends in Type MI cable shall be 
so made that the cable will not be damaged. The radius of 
the inner edge of any bend shall not be less than required as 
follows: 

(1) Five times the external diameter of the metallic sheath 
for cable not more than 19 mm ( 3 A in.) in external 
diameter 

(2) Ten times the external diameter of the metallic sheath 
for cable greater than 19 mm (% in.) but not more than 
25 mm ( 1 in.) in external diameter 



332.30 Securing and Supporting. Type MI cable shall be 
supported and secured by staples, straps, hangers, or similar 
fittings, designed and installed so as not to damage the 
cable, at intervals not exceeding 1.8 m (6 ft). 

(A) Horizontal Runs Through Holes and Notches. In 

other than vertical runs, cables installed in accordance with 
300.4 shall be considered supported and secured where 
such support does not exceed 1.8 m (6 ft) intervals. 

(B) Unsupported Cable. Type Ml cable shall be permitted 
to be unsupported where the cable is fished between access 
points through concealed spaces in finished buildings or 
structures and supporting is impracticable. 

(C) Cable Trays. All MI cable installed in cable trays 
shall comply with 392.30(A). 

332.31 Single Conductors. Where single-conductor cables 
are used, all phase conductors and, where used, the neutral 
conductor shall be grouped together to minimize induced 
voltage on the sheath. 

332.40 Boxes and Fittings. 

(A) Fittings. Fittings used for connecting Type MI cable to 
boxes, cabinets, or other equipment shall be identified for 
such use. 

(B) Terminal Seals. Where Type MI cable terminates, an 
end seal fitting shall be installed immediately after stripping 
to prevent the entrance of moisture into the insulation. The 
conductors extending beyond the sheath shall be individu- 
ally provided with an insulating material. 

332.80 Ampacity. The ampacity of Type MI cable shall be 
determined in accordance with 310.15. The conductor tem- 
perature at the end seal fitting shall not exceed the tempera- 
ture rating of the listed end seal fitting, and the installation 
shall not exceed the temperature ratings of terminations or 
equipment. 

(A) Type MI Cable Installed in Cable Tray. The ampaci- 
ties for Type MI cable installed in cable tray shall be deter- 
mined in accordance with 392.80(A). 

(B) Single Type MI Conductors Grouped Together. 

Where single Type MI conductors are grouped together in a 
triangular or square configuration, as required by 332.31, 
and installed on a messenger or exposed with a maintained 
free air space of not less than 2.15 times one conductor 
diameter (2.15 x O.D.) of the largest conductor contained 
within the configuration and adjacent conductor configura- 
tions or cables, the ampacity of the conductors shall not 
exceed the allowable ampacities of Table 310.15(B)(17). 



2011 Edition 



NATIONAL ELECTRICAL CODE 



70-195 



332.104 



ARTICLE 334 — NONMETALL1C-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



III. Construction Specifications 

332.104 Conductors. Type MI cable conductors shall be 
of solid copper, nickel, or nickel-coated copper with a re- 
sistance corresponding to standard AWG and kcmil sizes. 

332.108 Equipment Grounding Conductor. Where the 
outer sheath is made of copper, it shall provide an adequate 
path to serve as an equipment grounding conductor. Where 
the outer sheath is made of steel, a separate equipment 
grounding conductor shall be provided. 

332.112 Insulation. The conductor insulation in Type MI 
cable shall be a highly compressed refractory mineral that 
provides proper spacing for all conductors. 

332.116 Sheath. The outer sheath shall be of a continuous 
construction to provide mechanical protection and moisture 
seal. 



ARTICLE 334 
Non metallic-Sheathed Cable: Types NM, 

NMC, and NMS 

I. General 

334.1 Scope. This article covers the use, installation, and 
construction specifications of nonmetallic-sheathed cable. 

334.2 Definitions. 

Nonmetallic-Sheathed Cable. A factory assembly of two 
or more insulated conductors enclosed within an overall 
nonmetallic jacket. 

Type NM. Insulated conductors enclosed within an overall 
nonmetallic jacket. 

Type NMC. Insulated conductors enclosed within an over- 
all, corrosion resistant, nonmetallic jacket. 

Type NMS. Insulated power or control conductors with 
signaling, data, and communications conductors within an 
overall nonmetallic jacket. 

334.6 Listed. Type NM, Type NMC, and Type NMS cables 
shall be listed. 

II. Installation 

334.10 Uses Permitted. Type NM, Type NMC, and Type 
NMS cables shall be permitted to be used in the following: 
(1) One- and two-family dwellings and their attached or 
detached garages, and their storage buildings. 



(2) Multifamily dwellings permitted to be of Types III, IV, 
and V construction except as prohibited in 334.12. 

(3) Other structures permitted to be of Types III, IV, and V 
construction except as prohibited in 334.12. Cables 
shall be concealed within walls, floors, or ceilings that 
provide a thermal barrier of material that has at least a 
15-minute finish rating as identified in listings of fire- 
rated assemblies. 

Informational Note No. 1: Types of building construction 
and occupancy classifications are defined in NFPA 220- 
2009, Standard on Types of Building Construction, or the 
applicable building code, or both. 

Informational Note No. 2: See Informative Annex E for 
determination of building types [NFPA 220, Table 3-1]. 

(4) Cable trays in structures permitted to be Types III, IV, 
or V where the cables are identified for the use. 

Informational Note: See 310.15(A)(3) for temperature 
limitation of conductors. 

(5) Types I and II construction where installed within race- 
ways permitted to be installed in Types I and II 
construction. 

(A) Type NM. Type NM cable shall be permitted as follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited in 334.10(3) 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

(B) Type NMC. Type NMC cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in dry, moist, 
damp, or corrosive locations, except as prohibited by 
334.10(3) 

(2) In outside and inside walls of masonry block or tile 

(3) In a shallow chase in masonry, concrete, or adobe pro- 
tected against nails or screws by a steel plate at least 
1.59 mm (Vie. in.) thick and covered with plaster, adobe, 
or similar finish 

(C) Type NMS. Type NMS cable shall be permitted as 
follows: 

(1) For both exposed and concealed work in normally dry 
locations except as prohibited by-334.10(3) 

(2) To be installed or fished in air voids in masonry block 
or tile walls 

334.12 Uses Not Permitted. 

(A) Types NM, NMC, and NMS. Types NM, NMC, and 
NMS cables shall not be permitted as follows: 

(1) In any dwelling or structure not specifically permitted 
in 334.10(1), (2), and (3) 

(2) Exposed in dropped or suspended ceilings in other 
than one- and two-family and multifamily dwellings 



70-196 



NATIONAL ELECTRICAL CODE 2011 Edition 



ARTICLE 334 — NONMETALLIC-SHEATHED CABLE: TYPES NM, NMC, AND NMS 



334.30 



(3) As service-entrance cable 

(4) in commercial garages having hazardous (classified) 
locations as defined in 511.3 

(5) In theaters and similar locations, except where permit- 
ted in 5 1 8.4(B) 

(6) In motion picture studios 

(7) In storage battery rooms 

(8) In hoistways or on elevators or escalators 

(9) Embedded in poured cement, concrete, or aggregate 
(10) In hazardous (classified) locations, except where spe- 
cifically permitted by other articles in this Code. 

(B) Types NM and NMS. Types NM and NMS cables 
shall not be used under the following conditions or in the 
following locations: 

( 1 ) Where exposed to corrosive fumes or vapors 

(2) Where embedded i